There are two main reasons that roleplaying theory is an inherently flawed field (that is to say, there actually isn't much sensible you can say on the topic):
- Most attempts at a universal theory tying together all strands of the roleplaying hobby tend to be geared toward justifying the author's personal biases in terms of play style. This is certainly true of GNS theory, as can be seen by Ron Edwards management of The Forge, if not his writing on the theory itself.
Even if theory authors avoid this trap, they still need to be aware that their own biases in terms of play style will have a bearing on what they consider to be a "good" roleplaying game - which is what roleplaying theory is all about. It does make sense to talk about "good" and "bad" roleplaying systems, but those labels are fairly subjective - even F.A.T.A.L. has defenders.
- A huge portion of the roleplaying experience is made up by elements out of the direct control of the game designer. Designers can specify which behaviours players should be rewarded for and which should be punished, and they can define a whole host of other contributing factors (setting, mechanical structure, prose tone, etc.) which colour the gaming experience but at the end of the day it's down to the people sitting round the table to control how it all play out.
System matters - it colours the players experience, and it defines the framework they're going to operate in - but if people want to play as cocks in jets, they will do so regardless of systemic or setting considerations.
The lesson to be learned from this? There is one thing, and one thing only you can sensibly say in terms of roleplaying theory: make your game as much like it is as you possibly can. That is to say, if you want crazy martial-arts combat, focus on that. If you want complicated personal plots relating to characters' painful backgrounds, focus on that. Every bit of the setting, and every die-roll, card-draw, match of paper-rock-scissors or protracted argument of the system should be dedicated to supporting your core idea.
Do not, under ANY circumstances, try to do everything all at once.