I get what you're saying, and half agree. However, I do have a couple of thoughts on it:
1) Just because four roles have been defined, that doesn't necessarily cover all that might be useful. Can we think of a fifth role?
2) Perhaps the flexibility angle is such that he can adequately fill-in for an additional member of any other role. So an encounter comes along, the players say "for this one we could reall use another controller" - so the mage fulfills the role of a controller for that encounter. Yes, he shouldn't be as good at it as somebody who is a controller all the time, but having an addiitonal oarty member who can supplment any of the roles fairly competently can't be a bad thing.
We just market it as "the extra character when all your role needs are fulfilled - you take a mage who can increase the party's strength in a given role should it be needed; or step in when the party's character of role X falls".
I had a more polished post yesterday, but my bad conection ate it. >_<
Anyway...
How about just giving this mage the ability to multiclass into any number or Arcane classes. It's almost like the bard can do.
But, if multiclassing causes too many problems when it comes to paragon paths and whatever, maybe just a feature (Spell Researcher?) that allows wizards to buy a special kind of power feats that add only a couple of daily/utility spells to their spellbook from other classes in a case by case scenario - to prevent overpowered combinations and to add flavor and theme to the feat (like Fey trickery, Infernal curses, Healing artifices, Fireblade swordmagic, etc).
If there's one feat per tier, and they add one utility and one daily for every level in that tier, that would add a total of 6 spells (levels 1, 2, 5, 6, 9, 10 for the heroic tier). Is that too much for a specific power swap feat? Perhaps two feats per tier, or maybe allow only Daily spells.
Here's an example.
Fey Curses [Spell Research]
[Heroic Tier Feat]
Pre-req: Cha 13, wizard, spell researcher class feature
Benefit: You add the following warlock spells to your wizard spellbook: Curse of the Dark Dream, Crown of Madnnes and Curse of the Black Frost. You may prepare and cast these spells as if they were Wizard spells of the same level.
Perhaps each feat could ask for a pre-req in the same class, so learning epic warlock spells means you have to buy feats for the heroic and paragon warlock spells too, wich makes retraining harder to do.
Also, add some feats/features/paths that allow him to use Intelligence instead of the original ability (kinda like Intelligent Blademaster).
Well, as I said earlier, if you keep adding more options to the base wizards class you will eventually end up with the option to play a generalist anyway. But to contribute further, I have an idea within that framework to create a cost and advantage for a generalist mage.
Create a feat that allows the wizard to put more spells in his book, with the stipulation that this does not give him more spells that can be accessed at any given time. He will have to choose his at will, encounter and daily spells during the time in which he rests each day. If you want more of a cost, you could make one feat to do this at each tier. Then, you can create another feat that would allow him to swap one prepared spell(assuming that it hasn't already been cast in the case of encounters and dailies) for another in his book as a standard action.
And to give some idea of some alternate builds you could add to the wizard class, allow me to pull up some stuff I posted on the WotC boards:
School of Shaping - Battle spells would involve shaping the battlefield by various methods such as the traditional "Wall of" type of spells, stone shape, gust of wind, maybe a few illusions here and there... The idea would be to either, force, coerce, encourage or trick the enemy into going where you wanted them to go. This could be used as a form of the defender role, or it could be a way of funneling the enemies into a small area to set them up for a trap or AoE.
School of Evoking - Pretty much this is a wizard striker. It worked in previous editions and was never particularly overpowered(just about any powergaming wizard player would tell you that save or die was where it was at, not direct damage), so I see no need to fix what was never broken to begin with. You know the drill. Damaging spells of various types, shapes and sizes. Nothing more to be said about it really. So let's move on to...
School of Warding - Kind of like the old abjurer. The bread and butter of the school is buffs and debuffs, with perhaps a few illusions thrown in to trick the enemy into attacking false images and such. This school isn't for everyone, for although it could possibly turn the tide of a battle, it isn't particularly flashy.
After all, we have more than four monster roles - and the PC 'controller' role doesn't match the monster 'controller', it matches the monster 'artillery'!
Usable fifth roles might include lurker or skirmisher (arguably these are differentiations of striker), or possibly Brute (which might be a good representation for a Barbarian)
So, at the end of the day I think it'd be fine to give the wizard access to _most_ arcane powers - the actual "striker" elements and defender elements are often buried in class features, not the powers themselves... I mean, diabolic grasp and otherwind stride are clearly controller-like powers for instance.
I'd say do it on a conditional basis, though, looking at each power in turn and adjusting the stats appropriately. Like Diabolic Grasp, make it Int to attack and Con for # of squares and Otherwind Stride Int attack +Dex for # of squares, that kinda thing.
The swordmage powers that mark enemies or make them take damage to attack people other than the caster? Yeah, no, those shouldn't be available.
I guess I should clarify my argument a bit better.
IMO, there are two possible paths that the original question can take towards a solution. One assumes that the term 'generalist' is an accurate description for what a mage was in previous editions, whilst the other attempts to emulate what a mage was in previous editions and assumes generalist isn't the most accurate term.
I'm in the camp that thinks generalist isn't the best descriptor for what best represents magi of previous editions. If you go with the mage as a generalist then yes, I'd agree everything I've said so far doesn't apply.
IMO and putting it into 4e concepts, mages had controllerish and leaderish and strikerish powers in previous editions. Their spells tended to either do a lot of damage to one target, a fair amount of damage to lots of targets, or limit/control one target, limit/control lots of targets, or add buffs to the party.
So I sortof got ahead of myself and went straight towards improving the wizard as a controller, which I saw as its main role in previous editions. If you were to ask me to define the wizard in 4e terms and to base it off previous editions, my answer would be "Controller, with secondary striker and tertiary leader abilities."
After all, we have more than four monster roles - and the PC 'controller' role doesn't match the monster 'controller', it matches the monster 'artillery'!
Well, I'd agree that the wizard in the PHB doesn't really suit the controller role. As we all know, Mearls admitted they still hadn't quite nailed down the concept with the wizard. I do believe, however, that they've nailed down the concept with other controller classes.
That essentially amounting to pushing, pulling, sliding, immobilising, dazing, slowing, etc.
2) Perhaps the flexibility angle is such that he can adequately fill-in for an additional member of any other role. So an encounter comes along, the players say "for this one we could reall use another controller" - so the mage fulfills the role of a controller for that encounter. Yes, he shouldn't be as good at it as somebody who is a controller all the time, but having an addiitonal oarty member who can supplment any of the roles fairly competently can't be a bad thing.
But was that what you were really after? Did you want to emulate what the mage was in previous editions or did you want to create a jack-of-all-trades?
I'm in the camp that thinks generalist isn't the best descriptor for what best represents magi of previous editions. If you go with the mage as a generalist then yes, I'd agree everything I've said so far doesn't apply.
Allow the mage one at-will, one encounter power and one utility power from a class that fills each of the roles--defender, leader, controller, striker. The mage can prepare one of each (two at-wills).
Now replace the dailies with an ability that as a minor ability, allows the mage to swap one of the known powers with another. That would provide versatility at the expense of the most powerful abilities.
A few things to think about, theres a couple of ways we could get a generalist feel
1. Do we just give him a wider selection of spells (from strikers, defenders and leaders?) but the same number in uses and choices.
2. Do we give him a wider selection of spells to cast but the same number of uses (also would these be chosen on the fly or after resting?)
3. Do we give him a wider selection of spells to cast and more uses of them?
I quite like option 2
And here's one way I could see it working
the "mage" would have to pick up an encounter power from the wizard class and then another encounter power from another arcane class, he could use one or the other each encounter.
He could do this for Encounters and Utilities (utilities would have to have the same type either encounter or daily).
He would pay for this by losing his dailies as they are but instead would be able to choose an encounter power (up to the level of the daily he would have got) from an arcane class which wasn't the wizard and only be able to use this once per day.
If you add in the prereq to be taken at level one of needing to spend a feat and also a stat restriction I think this would work out well.
Not entirely sure what I'd do about paragon paths at the moment, though it'd probably go along the same lines
A few things to think about, theres a couple of ways we could get a generalist feel
1. Do we just give him a wider selection of spells (from strikers, defenders and leaders?) but the same number in uses and choices.
2. Do we give him a wider selection of spells to cast but the same number of uses (also would these be chosen on the fly or after resting?)
3. Do we give him a wider selection of spells to cast and more uses of them?
