Have you ever walked in a home depot? tile section?
you can get it there...
and, i don't know if I agree with anything else is a bad idea....
I mean, 1/2" cement board screwed to 3/4" osb t&g has gotta have some
rigidity to it... but, if your not installing 3/4" solid hard wood taht joins to the ceramic, ditra offers a lower profile of overall finished height.
Life is an experience... Learn from it!