i like the idea because it's sometimes a bit awkward running into an old friend that knows you but they have a different name/sig/ava but i still feel like paying for a name change is pointless if everyone can see what your name was before.
in my 6 years on this site i've seen people get name changes due to bullying, fixing a bad original name, and even just to step out of the spotlight. that being said i would love to have this feature personally but i don't think it would be fair to a lot of people that get legit name changes so i have to vote no on this one.
it is a good suggestion though and good luck with your thread man! this is just my opinion!