I think it would be neat if Arena could be further customized with being able to choose the card sets you want to use.
How about this for a separate mode from regular Arena:
After choosing your Arena class(among three), select the card sets you want to draft from. If you have picked Demon Hunter or Death Knight, then the relevant expansions with cards for these classes will already be pre-selected.
But you can choose extra expansions or even all of them for something completely wild.
Your AI opponents will have access to all the sets you have selected prior to drafting and they will rise in difficulty with each won match.
This would not work against human opponents because creating too many lobbies will impact matchmaking and cause long queues. But against the AI who drafts from the same sets you do, why shouldn’t it work?
What do you think, guys?