I would like a battle frontier, but one more similar to Emerald's, but with co-op more readily accessible due to it being an MMO. I liked the challenge of getting the symbol by getting to the brain and winning, not by grinding for it. Alternatively, the silver symbol or maybe a new bronze symbol could work this way, but the other symbol(s) would have to be earned. The battle dome could also have an option for an all players tourny; that would be REALLY cool!