Commode separate from sink & shower or at least where 2 people can be doing different things at the same time
That's probably going to be your downfall. Square feet is precious in an RV, and designing a floorplan like you want wastes a lot of square feet. Way back when, my folks mini-motorhome didn't even have a separate shower - you sat on the commode to take a shower - but the bathroom took up minimum square feet. Later my three different RV trailers at least had a separate shower, but none had a separate room for the shower or pottie. So unless you're looking at super-luxury huge RVs, I doubt you'll be able to find a floorplan with your pottie/shower requirements. Even having the lavatory outside the shower/pottie room is rare.
Click on the following link, then scroll down to floor plans in "luxury" Mobile Suites 5ers, to see some bathrooms you descriped:
Mobile Suites - DRV Suites
Go to new-RV manufacturer's websites and study their available floorplans. Find a floorplan you like and then see how many years that floorplan has been available. Some manufacturers include previous model floorplans for several years in the past, so you might find exactly what you want in, for example, a 2008 model. If you find a floorplan you like, then search the used RV websites looking for that exact model number.
Of course, if your budget is high enough to afford a new RV trailer, there are several manufacturers that will allow you to modify an existing floorplan to meet your needs. Excel is one.
Mobile Suites (DRV Suites) is another.