A "witch" in the Christian witch-hunt sense is not using an arcane powersource but an infernal one. The Christian worldview does not contain a morally neutral source of supernatural power. (
This is largely true, but I think it would be more accurate to say that the (Medieval) Christian worldview simply did not differentiate between "arcane" and "infernal;" arcane
was infernal.
Anyway, on-topic, I think I would have been more on board with the idea of power sources if they were more mechanically distinctive. As it was, classes from some power sources (like Primal) barely seemed like they had anything in common with each other. The paladin and cleric did have strong Divine associations, but that was more because of the history of the game.
Agreed. This was one of the biggest design flaws with 4E in general: not enough meaningful differentiation, and
deep differentiation, between the classes. An "arcane blast" was little different than a "martial blast," except in terms of flavor ("Ooh, shiny sparkly things" vs. "ouch, shards of metal").
It just seems that this would lend itself to "modularity".. you pick a base "class". If your character is primarily a combatant, you start with a fighter base. If an arcane caster, a mage base, etc. Then you build on the base whatever you wish.. rogueish stuff, arcane stuff, divine stuff. Fighter base + arcane trappings = swordmage; fighter base + divine stuff = paladin; psion base + divine stuff = "divine mind" (or whatever)
Why does every class possibility need a full separate class write-up in the PH?
I agree with you in theory, although having a bunch of classes is just plain
fun (e.g. I'd rather play a ranger than a fighter with nature skills). That said, I could see going with something like you describe above; adding in themes and you get all kinds of interesting combinations. It could even be that "ranger" is a theme and not a class, but I don't expect them to be that bold.
A lot of this hinges upon what themes will be, what ground they will cover. If they're broad and diverse then you really do only need a half dozen or less classes--at least the Holy Quaternary, but maybe no more.
That said, a monk is not simply a differently themed rogue, and a ranger is more than a hippy fighter. It will be tricky defining what is a theme and what is a class, but it may be that a class is a relatively simple affair and a theme provides further differentiation and detail and flavor. But one thing that themes do accomplish is that they take away the need to create a new class every time someone has a new flavor idea for a class; e.g. no need for a "Blackguard" class - that can be a theme for a Cleric or Paladin.
To put it another way, I'd keep classes as archetypes and themes as unique flavorings or templates over that archetype. Therefore you'd only really ever need a couple dozen classes, but could theoretically have hundreds of themes. I'd probably draw the line somewhere between paladin/ranger and blackguard/avenger/beastmaster--the former are archetypal classes while the latter are theme templates that further differentiate, detail, and flavor the character. Themes, then, could be modular options.