I know this is the right opportunity for someone with the right funds to make it big in the bitcoin mixing world but you do know right it is equally risky as hell ? There would be a serious reason why bitmixer decided to shut down.If not for the FBI notices or legal actions,they wouldn't let down a gold mine.Also,they were anonymous as hell.
I'm not saying you shouldn't take the initiative (community will benefit from it anyway) but think twice if you really want to give it a shot when things are quite heated at the moment.
P.S. You can try buying the source code from Bitmixer.Send them a message.