Allows players to mine landfill exactly like they would mine concrete. Nothing else, and absolutely zero UPS impact.

You can't mine landfill under entities, so mining landfill should always be safe. Bots are also able to safely pick up landfill, and the old water type is preserved.
This mod can be added and removed safely whenever without issues.

Known issues:

Placing bricks/concrete on landfill will return the landfill item, meaning you can technically fill in an entire lake with an inventory of bricks and a single landfill. Also mining one of these bricks will result in water and not landfill. (Technically a bug, but too hard to fix for me so probably not being fixed any time soon)