I am finalizing the tub deck and framing for the kids' bathroom remodel. The original layout called for just a flat tub deck framed with glass on one end abutting the shower and nothing between the other end and the toilet. I only have 140" to work with on that side of the room. Plumbing is already done so I'm not modifying the layout at this point.

I had an idea to put in a pony wall between the tub and the toilet to give some privacy to the toilet. I have it rough framed and I like the layout better with it than without it. The problem is that in order to give even just 2" of deck on each end of the tub ends (with 5" deck on each side) I would need to make the shower 35" wide by 45" long.

The idea I came up with is to frame out the pony wall above the tub deck with just dry wall on the toilet side and plywood, cement board and tile on the tub side with no stud in between (so a 1.75" wall essentially with a top plate supported by 2 2x4's and sides made up of 2 2x4's as well. I'd have to support the plywood at this point with metal corner brackets and I can glue it to the end of the tub deck. (See pictures).

Am I crazy to do this or do you think it will work?

Basically the tub side would have tile along the top 2x4, underneath that 2x4 and then on a piece of cement board attached to plywood butting up against drywall. I'd attach the cement board to the plywood with thinset mortar and then Redguard the cement board (just as I'm doing on the tub deck).

Thanks!