so I was thinking some sort of gate that is thick enough to have a little landing spot on top so the cats can land and then jump down. Like maybe a NIC squares and plywood combination.
I think this idea is worth experimenting with. Especially since you already have grids.
Rabbits often won’t jump over something if they can’t gauge what’s on the other side. So if you made a gate so it’s not see-through, it might deter your rabbit. You could put a landing shelf on the bathroom side of the gate out of the rabbits vision. If the cats are shown that once they would likely use it wouldn’t they?
Only problem could be a dare-devil bunny might copy the cats. Lol
I saw a friend recently that had placed the cats box inside the tub. Would that be an option? You might get away without having to use a gate then.
Someone posted a device here once that you put on the cats collar. It allowed cats to go through a pet door but not other pets. Pretty good idea! Knowing determined rabbits though, they’d loiter and wait to make a break in as the cat uses the door.