The Mahiki was actually banned because people continued to misuse its power long after an actual statement was made (and to be perfectly honest shouted from the rooftops) regarding how it was supposed to be used. In essence, people didn't take the second chance the Mahiki had seriously.
On the subject of another Kanohi; the rule, strictly speaking, is that you can only have one mask. If you want to replace one, that's fine. But you lose the old one. In the event of, say, someone taking Vakua's Suletu it would be a different matter because it's not a mask taken for personal ownership, rather it is one delivered as part of a staff-created bounty.