An actual to scale floor plan is what I would need to even begin to understand what you want. My gut says no free standing tub will fit I have no clue how long someone would live if they came to use the toilet while I was in the shower but not long. IMO separate toilet spaces inside a bathroom are just plain silly so no to that idea for sure. A door on the batrhoom is a must IMO .

I actually prefer a separate toilet room (hubs and I prefer privacy when using the toilet), but I don't care about shower/tub being in the same room as the vanities (actually I really dislike tubs and showers together in a separate space because #2 stinks and I don't want to shower in a stinky room). I would put a door on the bathroom. What you do inside the bathroom is personal preference. Maybe this isn't a problem for you, but my hubs & I wake at different times, and I would not want to be getting ready in the bathroom with a wide open door while someone's sleeping. Might not be your situation, but when you sell it might hurt resale.