Basically, the suggestion here is to make a new game mode, where you fight increasingly more difficult waves of enemies with a customized party. This can also be expanded to work in multiplayer for up to 4 players. I envision the mode as following:
1) You can select up to 4 characters
2) Killed enemies give experience to the entire party and drop rare+ loot and combat consumables, which are automatically added to your current run's arena chest (accessible before starting a new wave)
3) Characters revive, fully restore HP and spell slots after (long rest) every wave end and you're able to change your equipment
4) Waves function like this:
a) Starting enemies are spawned and you can prepare and open on them
b) For 2-3 turns, additional enemies are spawned, with Boss spawning on final spawning turn
5) Every opponent level spawns an additional enemy and increases enemies' overall toughness
6) All enemies have to be defeated in order to progress to the next wave
I think this would give the game a new dimension and make it playable for longer. All enemies and bosses are ones from the main game, can be in random or predefined order, with "infinite" scaling.
