Glad you found the feedback useful (and thanks again for yours on Abyss of Oblivion).
1. Those all sound like interesting ideas. Intuitively I think giving rewards/powerups that are NOT locked to the card used might be good, as you probably wouldn't want to create a sunk-cost feeling in players that works against experimenting with new cards/setups.
2. Totally understandable. If I'm being honest as well, Floors 11 - 20 in Abyss of Oblivion I've only ran through once or twice as well. lol
3. Totally understandable as well.
4. If I recall, the 3x6 tiles in MMBN were all vanilla-colored tiles with red/blue frames that don't reflect the maps on which the battle occured, right? If you could afford a different set of assets (just one) for battles instead of feeling the need to stick to the map tiles, it might give you more freedom to do what you need to do. Just a thought.