If that space was mine and I could tear it up and make it a grow space, I'd take it down to studs, remove all the shower stuff, and put up walls and electric. Convert the sink to a regular faucet and hose, maybe even RO filter. I'd take full advantage of the drain in the floor. That's a dream amenity to have in a grow room.
If I couldn't tear it all down to studs I'd build some sort of system to still use that drain and cover the walls & rest of floor. Get a hose adapter for the sink faucet. Basically just get rid of the tent and open up the space. May need to hang some
panda film on the doorway to block light cracks too