The bugged terrain could probably be fixed by having a bit of inertia. Instead of instantly slowing down when walking up a slope you gradually go from full speed to climbing a hill speed. More agility or athletics could make climbing easier. What really annoys me is how some buildings are bugged so no matter how much you're wearing or how mfast you go normally you get slowed to a crawl while inside that building. I remember a vanilla map with this problem, but I don't know if it had a name.
Better hitboxes would be nice, adding different hitboxes to weapons themselves would be neat too (I think either WOTR or Chivalry does this). Swinging a halberd, for example, normally does cut damage right? Well if you hit them with the pole part of your polearm it shouldn't be doing piercing or cut...
Perhaps they could also incorporate the length of the weapon and the range at which the weapon strikes into a damage calculation? Generally, the part of the weapon that swings the fastest is the very tip of the weapon because of the circular motion of the swing. In baseball a baseball bat has an area somewhat near the end of the bat (but not the very end) where it's optimal to hit the ball, and I don't know much aboot medieval sword fighting and such, but I'd think that a similar principle could be applied to a club or a sword (although they have other dynamics, such as curve of the blade, but that's another story...)
Honestly though, instead of be base 'damage' values currently in, I wish it incorporated something a bit more dwarf fortressy.
This is what I'm referring to. As you can see, weapons have a 'contact area' and 'penetration' value instead of simple a 'damage' value. A weapon with a small contact area (how much surface area the weapon hits with a particular strike) but a large penetration value would pierce a target (Look at the awlpike in Warband and think of how that weapon would work if it didn't have Warband's damage model). Similarly, a hammer could have a small contact area and penetration value, but because of the weight of the weapon (usually represented by 'velocity' in that table, but in that game the material of the weapon is a factor too...) it will probably fuck you up. Note the lack of 'piercing' weapons, they either have an edge or are blunt, the piercing comes into play with contact area and penetration. An edge weapon with a large contact area and little piercing (a cut weapon in warband) would probably glance off unprotected areas on plate armor. Just look in the 'details' under the table.
About halfway through writing that bit I realized that's probably a bit more complicated than necessary, but
something other than 'this weapon does 3 more damage so it is better' would be nice.