Wet Flooring Replacement Question

RetroActv

I have a 15 x 15 section of flooring butting against the corner of my tub that I'm going to replace. Looks like the wood underneath is 3/4 OSB. The wood isn't wet any longer, but it is warped, and I want to get the tile on flat and sturdy this time. The floor is ceramic tile. There is also what looks like another 3/4" OSB underneath the first layer.

Is it possible to do the tear out and re-install 1/2" OSB and then 1/4" cement backerboard on just this section? I'm not interested in tearing out the whole floor, as it doesn't need it. But I would like this section to be permanently reinforced and prevent any further complications in this area. A good mortar job and grout will help with this, obviously, but it can't hurt to reinforce with the backerboard, I figure.

Thanks for the help!

Floorwizard

Sounds like a plan. Although I would want to make sure you will install concrete board throughout the entire area right?