Team roll out vinyl? It's like the opposite.

For bathrooms in my house, I love rollout vinyl now. It's cheap, easy, 100% waterproof and super comfortable.

Followed by... Putting down something other than tile.... I hate tile on the floor. Shower walls, backsplashes, etc. are great, tile floors suck.

With enough time and money you can do anything.

That being said, 4" not enough to support the weight of a building. You could pour a foundation around the slab and build off that, leaving the slab the inside floor.