I suggest optionally (for example, through the startup settings) to disable the ability to spavn:
- volcano - on reinforced concrete.
- monsters and underground burrows/holes - on normal concrete.
- no updates for other (cheap) floors: landfill, stone, as well as crushed stone or wood floors from other mods - nothing changed here.

Why: if you play with a bunch of mods + mods that take the player somewhere far away, or on a different surface (for example: SE), you will not have the ability to quickly react to the appearance of enemies right in the center of your base.

But: you can invest in mass concreting the ground everywhere, and avoid enemies suddenly appearing in your base.
Cons: it is very expensive for stone and causes the pollution cloud to spread much farther than your walls.

In order not to make complex logic to search for empty spaces, if the selected area (from the previous logic) hits concrete 2-5 times — just make an enemy wave on the walls

Perhaps the option in the settings should be designed not as a checkbox, but as a dropdown with a choice of the floor on which you are not allowed to spawn enemies and volcano.
- None (disabled)
- Concrete (enemies) + Reinforced Concrete (volcano)
- Stone (enemies) + Concrete (volcano)

If possible, implementing concrete or other paved materials as an option would be nice.