As much as I do like having set, definitive units for things and even do enjoy the idea of precedents, the basic concept has a similar issue to stat-based roleplay. You can put on formal limits all you want, but at the end of the day, the more you add, the more you cut out a bit of creativity. I created an Airbender in Avatar, for example, that used a technique I don't at all recall ever seeing that involved using air as a pressure cutter. It was his signature fighting style. Yet, even though it should be possible in the world of Avatar and wrote out well, there was no real precedent to compare it to. At that point, you just have to monitor progression and really consider the applications and uses of things. 

There are also many more factors to abilities than just plain skill, and that's something to consider. I absolutely hate characters that are wrote out as dim-witted, dense or bull-headed immediately coming up with amazing battle plans, complex strategies or instantaneously performing the most intricate action that would perfectly save their ass in an engagement. That takes away so much from the characters that DO have those qualities. For instance, Naruto isn't bright, but he applies what he knows well. Shikamaru was ALWAYS the better strategist, and both Naruto and Shikamaru could probably come up a different method than someone like Sasuke that is considered a genius. Yet, one of them would have to, logically, have a better plan, and I would say it should be Shikamaru in most cases. That's using some examples I feel most people might know.

[b]Addition[/b]

I hate the idiots that try to correct your correct grammar. Outside of IC, correcting grammar is normally rude (unless it's a long-term misuse), so correcting already-correct grammar is literally being a rude idiot.