I get really bored sometimes and make unrealistic goals only achievable in trainer, like "no towers, maximum quanta, minimal turns to a win" or "how much damage can you possibly deal in 2 turns if quanta is not an issue?" or "can I build a deck which wins before the opponent ever plays a card (silence deck)?". I even had an excel spreadsheet for the second one so i could calculate just how much I was going over the 200 HP the false god had (I know I broke 600 at one point). Specific features I would like to see:
* ability to adjust own and enemy health
* option to loosen the quanta/card restriction - this could lead to some very interesting decks, like 50 Damselflys and 10 Shards of Freedom
* include the ability to play with arena options for yourself - there are things you can do with an Arena deck that are too difficult to do with a standard deck, like setting an Aether mark to 3, put in Fractals, and build the deck around something you want fractaled on the 4th turn. it's hard to get your card ratio perfect with only a win/loss record as feedback.
* more statistics - I wouldn't mind playing an entire match where, instead of HP, you score points. Scoring could end when one player is out of cards or both players (negating most of the speed deck's advantage).