I'm very aesthetically minded as a player. I like mining out large area's and building walls from scratch out of the same materials to make it uniform. But if you do this, your unable to wall carve. So the history is lost to the ages. What I would like to request is a second build wall choice that builds walls that are suitable for smoothing and carving. Either as build rough wall or build smooth wall.
All dwarven constructions are of the highest quality. We should be able to out build nature and make our fortress better than just smoothing out the mountain. It should be a monument to our civilisations power that not only did we carve out our halls but built and engraved them in the highest quality metals and brick. engraved with our cultures history.
Anyway thats what I'd like. If you'd be willing to.
There is a more advanced suggestion I have but It would take more coding than creating tweaked versions of build wall.
If you took build wall and made it rough stone. but rough stone could either be smoothed or fortified (works on natural stone too) with that design You could have a tree for more specialised uses of walls where fortified walls are harder to break but smoothed are more pretty and can be engraved.
But thats a lot more work so... I'd like the first at least. but if you have time maybe at the end of this massive masterpiece you could add the second. As its not important (as you could just mine the tile then choose the wall that is what your going for)