Calling for severing a finger to use a feat is waaaaaaaaaayyyyyyyyyy too much to ask for. Most characters only get 5-6 feats for their ENTIRE existence. A feat you can only use 10 times (maximum, without a regen spell) seems to me a way to say:
"This is the wost, stupiest feat ever & I want to make darn sure no one will ever, ever, take it."
Then, of course you'll just get some min/maxer to play a troll archer & make the whole reason for outlawing it seemingly obvious.
Just house-rule you don't like the feat, you don't alllow it in your game. Makes better sense to me.