It seems like the nature of programming is such that the game will never be able to keep up with the player's appetites for new content. At least not on its own.
So you have two choices, either program a certain philsophy (or batch of philosphies) into the game engine, or program a sort of forum where people can contribute new philosophies. Programs are inherently linear, they only go from one line of code to another line of code, but philosphy isn't linear. Algorithms can't make intuitive leaps. The game has to force a particular philosophy on the player simply because any game that didn't would be a perfect simulation of reality. . .and if that's what you want you could just walk outside.
The real question is, what philosphy do you want people to play through?
That being said, most games seem to pick one or two basic skills to focus on. FPS pick hand/eye coordination and spatial awareness, RTS games pick hierarchical strategy and team coordination, RPGs pick memorization and the ability to waste your life (lol). I think a philosophy game should pick a couple skills that would make people better at philosophy in general, rather than one philosphy in particular.
For example, the game engine could be taugh how to string words together into sentences. Then players could be confronted with NPCs who spout plausible-sounding gibberish, and the player has to learn to distinguish what makes sense from what doesn't. Maybe they could pick from drop-down lists of the definitions of all the words in the sentence (or at least the major ones) and they could quickly piece together an explanation for why the sentence contradicts itself. That would reinforce the notion that it is important to actually understand the meaning of the words so that you know when someone is saying something stupid. The reward could be stars. Everyone loves stars.
Another basic skill the game could test people on would be elementary logic. That's all based on rules so it could be programmed into the game. NPCs could make arguments that have logical flaws and then the player has to craft a quick analysis that exposes the flaw.
Even a game as simple as matching tiles could work. You know those memorization games where you have to find the two tiles with a clover on them, or whatever? Well, instead of that have one tile that has a fallacy on it and another that has the definition of the fallacy, or an example. The player has to not only remember where each was but has to learn the definitions and examples of common fallacies.
Yeah, philosophy is all crazy mystical and whanot, but there are basic skills (equivalent to hand/eye coordination) that help one navigate it.