A dungeon with respawning enemies that get harder and harder as you go deeper, would be a great addition to the game, especially for end game. Maybe even randomize the enemies, perhaps based on especially hard-to-beat enemy group templates
Definitely a good project for a mod, as long as it can be shimmied into the main campaign.
I agree that it is problematic that resources are finite for certain types of crafting but not others.
The economy is also out of whack. Things are way too expensive. At least that's the feeling I'm getting playing through Cyseal.
