That's actually a very good point. Probably should have handled player death like this. My next game will allow you to simply carry your whole party into a dungeon, so the reserve mechanic kinda gets removed. Instead there will be an item which allows you to retry fights, instead of getting a Game Over.
It's a sequel to Beatdown Dungeon. I felt there is a lot to improve, plus I want to add more characters. If you're interested, you can check out my Twitter profile, since I document the development process there: https://twitter.com/beatdowndungeon