Cool
When SJ first announced years ago that there would be extended fighter talents in the new TFT (eventually revealed as weapon expertise/mastery), I was hoping it might be along the line of your "feats". An extended list of combat talents or perhaps a set of guidelines allowing fighters to create their own "special moves". Fighters could then have a wide range of high-level combat talents that better match them with the capabilities and cool-factor that wizards get through their large spell list. Almost like fighter "spells".
For example, what if there were combat talents that allowed special and distinctive moves
on an infrequent basis, eg once per day or at a cost of X fatigue:
- slippery -- move past a front hex of an opponent (ie ignore one engagement during movement)
- spin attack -- attack two opponents even if one is in the rear
- reversal -- as an action, disengage through an opponent and end up behind them
- steadfast -- ignore forced retreat
These are all extremely powerful special moves. But that is the point :)
To maintain balance, there would be (a) a talent cost to pay, and (b) a way to limit their frequency, eg by simple fiat (once per session/day) and/or with the guidance from a better mind, an appropriate fatigue cost (eg loss of 3 ST as fatigue to do a reversal?)
It would be nice to balance things so that the motivation for a player to choose a special talent for their character would be, as you say, they make the character more compelling, unique, and fun for the player: Fafner can hold a bridge to the death, Mouser can never be cornered (at least until the fatigue kicks in). But the cost would be high enough not to pay off for the min-maxing approach (as now where basically all good fighter builds take running, for example; or dare I say all wizards take silver dagger wands).