Qud is a really good roguelike, which means what I'd want to change is pretty fundamental to roguelikes: the constant low-level fighting. Bumping into three dozen beetles to kill them is really boring, but I still have to pay attention, because the way I die most of the time is because I accidentally get myself into a dangerous situation without noticing. It's rarely the boss fights that kill, it's an accidental confluence of bad factors in generic play.
Most recently I died because auto-explore walked me straight in front of a monster with a freezing attack. The time before I died because powerful chain gun turrets have the same map icon as weak musket turrets. One time I died fighting a powerful boss with unusual abilities. That death was satisfying, the others were not.
These two bad deaths were avoidable, of course, but they require a level of constant attention and checking that is at odds with the low-level hum of hacking through generic enemies. And at least the chain gun one could be patched by making the more dangerous enemy visually distinct.
Instead of constant low-level fighting, I'd much prefer more rare, clearly delineated fights, setpieces even. XCOM, especially Chimera Squad, do this much better: you have a high-intensity fight where you know your choices matter, and then it's done. (Chimera Squad's writing is a bit meh, but I'm coming around to the room-scale battles it does. And the burger ads are funny.)
Setpiece fights can also remove the suspension-of-disbelief problem where the compatriots of the enemies you're fighting don't join in despite being next door.
The main problem is how to integrate those fights into the map. If the game world is fully or partially human-authored, it's possible. Generating interesting and properly balanced fighting setpieces sounds rather harder.
More on roguelikes soon, I hope.