Second GC came by this AM-- much more laid-back and casual than first guy-- got him from Angie's List and had very good reviews but he brought nothing except a business card--no list of references, no generic copy of contract, no list of their subs or any sources they use... he was nice but a little unsure about the "professional" aspect... He said that he thought moving the toilet 12 inches to gain more shower room in its current location wasn't very practical for the money/use tradeoff since it would be difficult to enlarge the shower w/o cutting off the space needed to come into the bathroom...he said they could move the back wall of the shower down about 6 -8 inches and all space for a niche to hold shampoo and stuff which would help open up the interior standing space. The first guy thought it was doable but expensive but haven't seen his sketch/diagram for what room would look like if that was done... After talking to both these guys my husband is more open to just taking out the tub entirely vs putting in a 5ft tub (maybe a jacuzzi version)... which surprised me a good deal since he was adamant about it before they came... Our daughter on the other hand says she really misses not having a tub in their master bath and would never give one up... If we put the shower at the end where the tub is, it could be a nice, walk-in 4x5 shower and make a great focal point in the room... we could also turn the shower location into more storage and have some nice (rolling) laundry hampers added so I don't have to use closet space for dirty clothes--I don't like that... How many of you would be willing to trade in a tub you don't use--as least we don't--for a nice larger shower? Photo shows the entrance into wet area from the hall w/dual sinks--

A couple of things. With regard to the chimney stack, I recommend posting on the Remodeling forum of GW. With the existing closets in your bedroom and the guest room, could you totally take that space over and use part if it for an enlarged bathroom and the other part, a walk in closet oriented the other direction? The guest bedroom could have a closet built on the wall behind the toilet. Maybe thats workable maybe not. I would draw out all your dimensions on graph paper. Then taking tracing paper cut out to scale furniture (beds, vanities, nightstands, etc) and bathroom fixtures. Then place them around your rooms to see what fits and doesn't fit.

Oh dear, Kim. Just don't fall over in a dead faint when you get the demolition bill! That's a lot of tile. In a room that large, I would keep the tiled areas to only the wet areas. No matter how warm the color of the tile, it still looks cold to have that much hard surface. Here's some photos containing elements from the Craftsman style of your home. Some of these baths are much smaller than yours, but the ideas are there. The last photo is of a dual vanity with tower.

It is doable project to diy if you are properly informed. You seem to have an idea already. You are not cutting the joist...NO ONE should be cutting joist w/o first consulting a structural engineer...I think most curbless applications on upstairs bathrooms end up building up the subfloor (you already have) to the whole bathroom to accommodate the pan as well as deflection. Which is why you need to be well informed and follow the guidelines that were mentioned here by celadon or JuneKnow (think is the same person) hence why I mentioned John bridge and terry love. Those are forums dedicated to plumbing and tiling. There is a deflection calculator that work if you have regular joist. If your joist are engendered (I-joist) the Schluter also provides info on how to build up the floor. 720 deflection is for natural stone. 360 is ok for ceramic tile. What that means is the needed material on top of the joist to minimize movement. As far as making sure sure the subfloor for the shower pan is flat is so that the actual Schluter pan can do its job of sloping the water you are well informed. I followed the Schluter handbook and talked to the rep and so far it’s going great. You have to be at the ready when you post here I noticed. Seems like if you say DIY two or three common posters on this forum will right away chastised you for doing so assuming that bc it’s a diyer that they don’t know or are not aware of how to do things. Some of the recent post have been asking for help after their contractor did a horrible job tiling, lippage grout lines bigger than other, tile trim off or not centered, so I say better do it myself that have to deal with those issues. Here is a pick of my current shower. To clarify first and foremost, otherwise said ppl would just start saying how wrong you are and how it will fail!: buit up to 720 deflection for natural stone. Framed around I joist and supported between joist under shower pan. Checked plumbing on drain to keep the slope necessary after the p trap. Ditra uncoupling membrane on whole bathroom. Kerdi band around all seams close to the wet areas. Marble is honed. Will be sealed and then anti slip sealer added as well. Epoxy or spektralock1 grout will be used to further keep things waterproofed. Have already ran shower head and handheld and water slopes right to drain. Best of luck!