Don't steal my idea!!!!!!
So, if it has limitations, it's ok, but if it were somehow intertwined with the arena, like say the arena was...
Pit of Dispair-
Both battlers begin in the middle of a huge crater, meaning rocks, and dirt galore, no trees, grass, but a medium river runs through it. The Arena is aptly named for the challengers who have lost themselves in this pit and perished. A random basic/baby pokemon's spirit will attach itself to each battler to help fight along side, but can be ushered away after 3 rounds by the cleansing light. Pokemon may ask for assistance at a cost of 6% health per round, for 1 move.