I think being able to build pillars manually would be a great addition, so that we could connect base pieces that didn’t connect to the floor ourselves. It’s sometimes jarring to see a base room floating because it was placed too high up. This could allow for more aesthetically pleasing bases and open up some decoration possibilities as well.

I agree with this.
It feels awkward for the base to be off a cliff edge by a lot and it be just floating into the water.
It really breaks the immersion

yeah, sometimes supports are missing and sometimes there are a few too many. being able to adjust that would be appriciated