I necro this thread, because the suggestion is somewhat related.
1) Designate cleaning similar to smoothing, mining etc. (outside of water)
I second this. This should include broken bolts and should be applicable on walls, ramps, stairs as well. Outside cleaning should remove vegetation, you can't really clean grass without removing it (similar to dirt roads now). Yes, I want to clean the map - imagine you play in a beautiful white sand desert where no rain ever reduces the amound of blood on the map - skeletons all around are fine, but blood and vomit
2) Make blood/vomit decay over time (set a half-value period and check once a month).
Spreading, infection is all fun, but when you still have blood spreading out that was spilled a dozen years earlier... was washed of a hundred times, it gets old. When a corpse rots down to a skeleton there shouldn't be any blood of the beast left.
3) Remove fire resistance of vomit.
A fire of the vegetation removes blood stains, the vomit remains.
4) Fire should be able to spread modestly up and down ramps / walls. (Would help in clean-up, in many cases.)
5) There should be a possibility to remove mud from stone floor.
This would make life easier after flooding accidents.
6) Dry caverns behave oddly. (Bug?)
Nothing grows in dry caverns (even after finding a wet one later), but after being exposed to dragon fire things start to grow in the affected area.