4 classes with 30 themes is 120 possible combinations.
14 classes with 20 themes is 280 possible combinations. I want lots of combinations.
This got me thinking. Deep down, if I were building D&D for me only, I'd have a list of classes that included Paladin and Ranger, excluded Assassin, and I'd have a PHB that was satisfactory to me... but I might not have anyone else to play with, and that makes for a pretty sad game IMO.
I realized that, whether I do or don't like a particular class, or a combination of customizations that make X class look suspiciously like Y class, doesn't matter. If someone wants to play a Cleric that looks, to my eye, like a Paladin, or a Rogue that seems Assassiny, meh.
The more permutations, the more people will get to play what they want. If there's something that the DM/group thinks is a little ridiculous, it can easily be excluded from that game, without exclusion from the game.
My only reservation here is how themes are handled with regard to classes. Maybe I'm just too narrow in my thinking, but I think the core feel of the Fighter runs counter to the Magic-user theme, and that there should be some limits, but maybe that's just the realm of houserules.