This would be a nice feature. Make it a 1 time thing so people like me whose 5 year old made there account name can actually have a name. Also make it speaker WC so everyone knows BGB is now Know as KungFuMasta! my .02
This to me is a brilliant idea, besides its not like nobody is not going to know who you are or who you have changed to
There should also be a cost and NOT cheap maybe something like 400 - 500 gems (Come on Tynon if just given you a nice source for more income :P)