Interesting concept. The drain would need secured, you would need to install some hardware mesh so they are able to climb and have foot holds.
Off the top of my head one concern would be caulk, most shower stalls/bathtubs have some caulking, older caulking can peel back easily and be chewed on. Gliders will find any flaw and work at it, this could pose some health issues. Caulk is not used on glider wheels or toys not even fish tank sealer is used for gliders.
Now if your talkin tile, you have grout, grout will absorb urine and isn't the easiest to clean in normal circumstances.
The concept isn't a bad one, and would likely be easy to clean if you have a hand held shower head but there are some things to consider in order to make it a glider safe environment. I can probably come up with some other concerns that would need addressed after I've had coffees lol