Your idea is bad, yet you might turn it into something cool: Instead of really changing a name, you could change somebody’s visible name temporarily for let’s say one week. The pranked player still keeps his old name though so nobody can steal it. Make it expensive, 5 BP or so.

@Big Brother: I never suggested to permaban people, but to temporarily ban people from posting on Flamebate public forums. It is lame, but money is money.