I think learning to play left-handed would be the best approach, too.

I have a book of transcriptions of Django Reinhardt solos and the person who wrote it said he couldn't figure out how Reinhardt played them without the use of all of the fingers on his left hand. It's possible that he had some use of the remaining parts of his injured fingers.

I think it would be very difficult to play without being able to press the thumb against the back of the neck and the index finger is very important for fretting. Once could get along without it picking or strumming. Flatpicking is a very good technique, too.

Django Reinhardt was a very good guitarist; most people can't play as well as he did, even if they don't have injured hands.