If there were an easy way to regrow fingers, cutting one off would not be used as a punishment. The point of maiming a thief is to warn all who ever come in contact with him that he is a thief; it won't work if people can undo it. You can wear gloves with that digit stuffed with cotton (and make a bluff check) to hide it. I would not apply any combat effects.
You can make an adventure out of it.
Your character has heard word of an ancient ritual that will regrow lost body parts. Of course, you have to find the ritual in a tome in a long-lost dungeon, filled with all sorts of reptilian creatures. As the character gets the ritual and casts it, he discovers the finger that grows back is that of a lizard! (Yes, I totally stole this from the Lizard in the Spider-Man comics.) Question is, does he discover this in time, or does he find out too late?
Alternately, automaton fake fingers can be cool too. Maybe give it a special ability.
to reflect adjusting to loss of finger plus loss of one ring slot until the finger is restored.
This thread wants me to make a Warforged Rogue with clamps instead of hands.
I shall name him Clamps.
See, I might remove a ring slot if you started out with 10 of them. I don't agree that missing a single finger out of those 10 should cost you one of your 2 ring slots...
The rest of it sounds pretty much perfect: after all, he could have been killed instead of just maimed.
carnivorous sand