First off, I've only played arena 3 times and I really enjoyed it. I feel like it is very tactical, not frustrating, and also plays relatively quickly even on the unlimited time setting so there is no rush.
My suggestion is for the hero pool. Currently there are 4 preset heroes (which I would assume a few more might be added)
I would like to see a method of creating characters and saving them in that list to be played with. They would of course have the same power as the presets. You get 10 combat attributes to spend, etc. and Get to select X number of available abilities, select which item preset you want (staff, sword shield, etc)
One consideration would be that you need to know what abilities the enemy characters have, so either in game or during a pregame screen you need to be able to look at the opponent's abilities.
I think this could spawn a lot of creativity and prevent the arena from getting stale quickly from playing with a small number of presets every game.
