There are lots of vintage inspired floors that you can do that aren't necessarily lots of little pieces. Bill V shows a bathroom with a honed marble floor on the diagonal with a thin dark border and then a polished marble border beyond that. You can search around a bit to find his website and take a look at it. Also you might want to search back on claire de luna - she shows a similar look with terrazzo tiles and a border in a creamy and warm rather than grey and cool palette. This could be pulled off with travertine and coordinating ceramic and stone for a vintage but not a slave to period feel. You could also do a checkerboard with larger format tiles - either a subtle tone on tone checkerboard in earthtones or black and white for something more graphic that would pop. There are many ceramics out there that either look like stone or not but have colors that would look great together in a checkerboard.

Karenseb has an excellent point about the sound-insulation value of the closet where she put it. Bathrooms make a lot of sound! I am currently sleeping in the room that shares the wall with the shower and I hear every "clink" of my husband getting ready. Granted, your shower in Option 3 is not on the adjoining wall, but the general noisiness of the bathroom can translate through that wall. So no matter your choice of layout, you may want to insulate that adjoining wall for sound. If you are concerned that her layout shorts you on closet space, think again. I am seeing a 7'6" wall for your long one. You have to subtract 2' from that, though, since the closet has an "L" that makes the end where the two rods meet unusable. Same with the other wall, giving you 3 ft there. So I count about 8'6" of closet hanging space, though you might be able to squeeze in a few things in the corner. She is giving you right around the same amount in the straight closet. Get a solid-core door for that bathroom. If one of you ever has a job where you sleep later than the other, you will appreciate the sound insulation. The elbow room at the bathroom sink is worth this design, plus you will save some money in plumbing costs, having the showers next to each other. Her design makes good use of the bathroom windows, as well. And you can get two stacks of small drawers in her vanity, I bet!

After doing some research... what about using Ditra over the oldest tile after filling/leveling any cracks with thinset mortor? We plan to use small porcelain pennytile. The Ditra is 1/8" and says it "uncouples' the surface from the substrate. https://www.homedepot.com/p/Schluter-Systems-Ditra-54-sq-ft-3-ft-3-in-x-16-ft-5-in-x-1-8-in-Thick-Uncoupling-Membrane-DITRA5M/100143471 UPDATE— nevermind about this. pennytile doesn't work on Ditra. not enough support for tiny tiles. "Don't do it. I've seen hexes set over Ditra, with the flat trowel the day before method. The result? Lots of busted grout joints, and hollow sounding tiles. Seen the same with 1x1 and 2x2's also." Middle of the night research doesn't pan out. This is going to be much harder than the powder room unfortunately. We demo'd that room down to the studs but the substrate was just plywood. 😣😩

I'll be a contrarian. I would never knowingly rent a room with a shared bathroom in the hall. That would be a complete pass - I don't even like having to use a hallway bathroom in a sleeping situation in which I would share with friends and family because if I need to use it in the night I would have to wake up more/get more decently dressed and I hate having to shlep stuff to take a shower or perform normal grooming stuff in a bathroom. I don't have the horror of viewing a toilet from a bedroom that some houzzers seem to have. It certainly wouldn't bother me on a temporary basis. I have a master bath in my home and I can't remember the last time I actually shut the door. I don't have issues with smells or humidity but perhaps that is because my Toto washlet has a built in deodorizer AND I have an excellent Panasonic fan which runs based on ambient humidity levels. I don't generally even have condensation on shower doors or mirrors after exiting let along huge amounts of humidity wafting through my bedroom. The question really is one of economics. There is a cost to installing the bathroom and OP would need to decide whether they would make up the expense by having increased rent and/or renting it out more frequently. Certainly any prospective renter would see a picture and determine whether they wanted the ensuite with a curtain in the room or use of a bathroom in the hall. Also resale value is a red herring. At such point that OP wanted to sell it would be relatively inexpensive to convert the bathroom into a closet if having the ensuite in that room was a negative.