Mustrum_Ridcully
Legend
delericho said:If that's right, then the system will, indeed, be simpler. But it will come at the price of a massive hit in terms of the resolution of characters that can be modelled by the system, at least until the get around to giving us the Mageblade, and Priestblade, and Magepriest, and Arcane Trickster, and... classes. Class Training feats are good for doing "a fighter with a bit of wizard", or whatever, but they'll fall short when trying to sit in the middle of the two.
And yes, I know that 3e isn't good in this regard either. The "multiclass spellcaster" problem was #2 on my list of "must have fixes" for 4e (right behind fixing Level Adjustment). But saying "you can't play this way until we get around to it" isn't a fix of the problem, since it leaves us no better off than we are now.
If a majority of the abilities of a class are part of their list of powers, I think multiclassing will per default work better, because you can just exchange your Class X powers with your Class Y powers. In 3E, a lot was based on level dependend benefits - specifically BAB and Caster Level & spell slots/known.
A possible implementation for multiclassing in 4E might be that you just pick your "CLass Training Feat" and the next time you gain a power, you can choose a power from that class instead of your "normal" class. Unlike in 3E, you won't be forced to pick the 1st level equivalent of a spell if you multiclass at level 11, you can get a level 11 appropriate wizard power. But you will have to give up one of your class powers for it, which means it's an oppertunity cost.
Fly or Vampire Stealth Move?
Fire Shield or Warcry of Megadamage?
Lightning Blade or Healing Lorecall?
(Or whatever the names for 4E poweres will be

Well, that's just a guess. It might be that the Training feats work similar to this, but there is still a "real" multiclassing variant.
I also think that a customized class will always work better in implementing a new archetype (even if it's a blend of two existing archetypes) then any kind of multiclassing.