Have you fiddled with the idea of the following 3 challenge modes?

Challenge Mode Maximum - All cards are maximum level.

Challenge Mode Minimum - All cards are minimum level.

Challenge Mode RNG - All cards played are randomly leveled. (This is my favorite because it would cause huge chaos)

I don't play challenge mode anymore after the most recent change. However... if any of these options were used, I would actually be motivated to go play. It would create a really interesting dynamic ad I would love to see the decks people create.