What do you think about the possibility of building blocks of raw rock.

[Const67]

Now we dig them and create designs.
There is a suggestion:
Science - Add a study thread - the construction of reserves.
And such a skill is given not to everyone, but maybe to everyone.
As an option, the skill is given to the Duplicant trained as a builder 3 level + agronomist 3 level, and gets the opportunity - a new specialty "builder biome-reserve".

[Sasza22]

I think there should be a special tile type that could be filled with certain things to create a "natural" floor. Lets say we build this tile out of refined metal and it works like any other build tile but it can accept sand, dirt or clay and that makes it behave like a natural tile. It could be even dug out leaving the metal base to be filled with something else.