Your layout is not showing up.

Unless you will actually use tub in the master bedroom, I would not mess with a very successful design in order to stick one in. After all, you already have two other bathtubs in the house and it is not like you're talking about putting in an extra long or extra fancy tub in the masterbath to really jazz it up.

Actually, I wouldn't mess with the current design EVEN to fit in a FANCY tub that I figured I would use once a month. So I sure wouldn't do it to fit in a "standard" tub unless that tub was going to get CONSTANT (i.e. DAILY) usage. If mom just thinks she might want an occasional bubblebath, just tell DD that she'll have to let mom use her bath room on those rare occasions!

However, if you must have a tub in the masterbath, the way to do it with the least impact on your current design is probably to move the shower upward so that it sits beside the bedroom. (You would have to lose that transom window so would probably want to remove both transom windows on that side.) Then, stick the bathtub against the wall where the shower is now. You might have to widen the entire bathroom by a little bit in order to make room for a shower door beside the tub.

Something like this...

BTW, note that if you make the shower wide enough (more than about 6 ft from wall with shower head to opposite wall, and move the shower entry so that it is as far from the shower head as possible, you can probably get away with not having a shower door at all. Believe me, not having a glass shower door to try and keep clean is a major blessing!

On the whole tho, I would leave the design as it is and move beyond "preliminary drawings" to getting blueprints so you can actually start building! While it is good to spend plenty of time at the drawing stage, I think you've maybe begun to obsess a bit toooooo much. Time to move on to getting real drawings made and get started on making the dream into a reality. Obsess too long and your kids are going to be grown and out of the house and you and DH won't even need to expand. LOL!

Thank you Bevangel! I do use the bath everyday. I would miss my bath, it helps with my muscles/joints. Even though this will be the 4th bath tub (one upstairs too) I can't imagine starting my day by gathering up clothing to visit another location. Thank you ever so much for your "move forward" insistence. I was thinking he same as our prelims take a month at a time, each footprint change puts the build further into the future rather than the now. I am forwarding your diagram along with the other 2 renditions on our previous prelims. Then....actual blueprints:), well after electrical and lighting approvals. So excited, thank you!

HOS, on bevangel's nice sketch you might consider switching the locations of the shower and toilet -- the vanity could get a bit shorter.

Thanks Oaktown, We are trying to get the sq footage down as well as make it all "work". I did tell the architect a smaller vanity is fine after reading your post.

Bevangel, I'm really liking the doorless shower idea. I will resubmit your rendition. We just received ballpark figures from the contractor and we are good for up to 1360'. At 1306+changes as shown=1344. Should I just add 1 more foot to the depth of the living/kitchen area? Not sure if with 18x31' that we could do a table too. I do like the possible front drive visual. Thank you all again. We will be moving forward with blueprints soon.