So maybe instead of a mod where you are required to build flooring, what if like in the Dune C&C games, concrete is encouraged more than required? You can build a building but it'll degrade over time to low durability, unless flooring is placed under it? Maybe even lower crafting speed or lower % chance of quality?

There's a similar mod that does the opposite, having buildings on foundation makes them better, check it out! https://mods.factorio.com/mod/StableFoundations

I'd rather not add that mechanic to this mod because currently blueprinting works and doesn't make it a hassle to remember