Depends a lot on what you mean by "japanese soaking tub" -- I have an acrylic corner tub that has a seat and is deep enough to come up to your neck (maybe 30x30x30), but I'm sure some won't like the high leg over required to get in. If you were going whole-hog with a tub sunk in the floor or a wooden tub, I'd worry even more. Depends a bit on how long you intend to live there -- might not be worth worrying about the next person.

Big error for all. 32x32 is way too large for a small space, and a difficult to use tub inside a shower is a giant turnoff. Better to have a single nice shower with appropriately scaled tile than to waste money on a really poor concept.