Instead of respawning monsters, I'd rather have random encounters a-la Fallout 1&2 where you can bump into interesting scenarios while you traverse the map.
So even if you cleared out a map of all enemies, there's a chance that you'll meet a random stranger needing rescue, clumsy bad guys getting caught plotting something, bandits, etc. Not that this game really needs any more XP. It's easy to become OP from low levels.
