I quite didn't understand why the AD&D 2nd Players' Option was buried.
Because it was utterly and spectacularly broken? Using Player's Option you could easily create a Cleric who had access to your chosen half-dozen 'important' spheres, could cast Wizard spells from one school (pick: Evocation or Enchantment), use all weapons and armour, and use the Fighter attack bonuses.
It also had the problem that you build your class (and race!) at character creation, and then the choices were fixed. So, if you later decided you wanted to do something else, you were stuck.
And, what's more, it made character creation considerably more complex. This is fine for 'advanced' players, but it's a disaster for the base game, which really needs to be suited for new players as well (or even moreso).
Basically, the 3e model of starting with a base class, but then gradually customising with feats/multiclassing/prestige classes is a much better solution: classes could be (mostly) balanced, you still got the customisation, but initial character creation was (relatively) quick and easy.
Where they probably didn't go far enough was in the ability to customise your character as you levelled up... but with the hundreds of supplements published, surely everyone had the tools to build almost exactly the character they wanted?
1. 5e must have customizable class called "Hero" or something like that. Then players can just buy class abilities to make it like they want. If you wanted, it could be something like ½ fighter, 1/4 of roque and 1/4 something arcanish. To prevent this getting overboard, it should hard be to create something of equal strength compared standard classes.
So, if you want to be creative in the construction of your character, the system should punish you?
I think that's the problem with hybrid class-based/point-buy systems - either the point-buy allows easy construction of characters as good as the fixed classes (and so it gets wildly abused by munchkins), or it makes creating equal characters very difficult (and so it punishes creativity).
I think there's a place (especially in a modular system) for providing a point-buy creation method as an alternative in a supplement... but I think base D&D should remain class-based, and I also think it's a bad idea to try to mix-and-match the two systems.
4. Make divine magic feel more priestly. Not just that "I pray a bit and I cast spontaneous cures, otherwise I'm just like wizard". The servitude of the deity should be more evident.
Agreed. I'd be inclined to make Clerical magic mostly ritual-based.
5. I'd like 5e to have more surprise-elements, most of them pleasant. Everybody loves Deck of Many Things, so why not go from there?
Actually, many many people
hate the
deck of many things, the
wand of wonder and the like.
The fundamental problem with having permanent random side-effects is that they go one of two ways: if the group apply the tables as-written (and don't fudge), PCs find themselves permanently screwed up by a single bad roll; if the DM fudges the results, the tables become a 'shopping list' of beneficial mutations and effects to be acquired.
This is another area where I'm not opposed to such a system (especially in a modular game), but it should be strictly optional, and probably relegated to a supplement, not in the base game.