3x3, 6x6, or 9x9 (thou crafting panel needs a checklist to hide some) Kinda sucks scroll thru corner roofs, and angle, stonebrick (when your on t3) etc.
Walls that 3long, (with different design be nice) THOU, go to big… I guess base easier to break down. XD
If possible, if a foundation is 2x2 instead of 1x1, they should have double penalty on stability as well.
Instead of attaching 4 ceilings to a 100 stability place, it would only support two. Or used pillars are equally bigger as well (using up a whole foundation).
Instead 2x2 walls and doors would be neat too. A door which would cover a full foundation on the ground and goes almost up to 1.2 foundations. I think lots of people might like such doors, but I might be wrong.