We are also in the process of figuring out a redesign for our master bath so your plans appeared somewhat similar to ours. I would suggest though that if you have the space, rather than a 12" wall cabinet, make your vanity 72" and incorporate the cabinet space into the vanity area. 12" isn't very much room to even put a towel so I don't think it would give you a lot of storage. You could put a knee wall on the side of the vanity and put your toilet on the same wall. Move the shower to the other wall in order to make it larger. Without a tub, I think you have plenty of room for a larger shower.

4'x7' is a waste of space when it comes to a closet. It's not big enough for hanging except on one wall and a bit of the small wall. You'll get better storage in less space with a simple reach in closet with organizers. The bath itself also needs to increase in size if you want a soaker tub and a shower. A soaker tub isn't designed to work with a shower. You need a shallower tub with an integral tile flange to work with a tub/shower situation. A deep soaker tub will be a PIA to step into to use as a shower, and you'll have water infiltration issues if you try to use it as a shower as well. Also, most 4 bedroom houses would want to have 3 bathrooms. You may want to rethink your wants and needs and the small size of the space you are working with. One needs to reduce, or the other needs to enlarge. Since you say the budget is small, and this will be an expensive project, I'd suggest reducing some of your wants, and eliminating one of the bedrooms to better utilize the existing space split between the others. A 3/2 is a common configuration, and would give you more space to work with for the design. Remodels like this are costly because of working within the constraints of the old footprint and accessing the major systems. Also, integrating the old and new isn't always successful. It's just easier to do plumbing and electrical and HVAC (all of the expensive stuff) when the walls are completely open and you don't have to fight the old stuff into submission. It's one of the reasons teardowns of older homes in older neighborhoods became popular. It's less money, and you end up with more house that has more modern proportions and amenities.

Sophie, having just gutted two bathrooms and a kitchen I would have to agree. My master closet cabinets with island were significantly more than the cost the OP wants to spend on the entire project. And that was just the master closet. However, the OP should plan the space then get bids and access what are must haves versus what she wishes. I deleted the tub because I don’t take baths and I wanted a large shower. As long as she has a tub somewhere in the house it is not an issue. At that point, she will have a better idea of what her budget should be, but based upon the space I would guess closer to $50,000

You can do the tub/shower if you do a bit of a pony wall so that you have a corner in which to put a tiny sink and med cab on the right side of the shower. This set on Houzz is $650 and includes the corner cabinet with mirror. The vanity needs only 18.5" of wall on each side. I wonder if you could squeeze in a skinny wall in front of the last 20" of the tub in order to put this in front of it? Or would it be kosher to back it up to a glass tub enclosure? Or could you glass-block in the last half or third of the tub and back up to the glass block? Here are the smaller wall hung corner sinks available at Houzz. If not, you CAN squeeze a tiny wall-hung sink right next to the end of the tub, on the right. Hang a mirror or small recessed med cab above it, and put some recessed cabinets into the wall across from the toilet for toiletries. Just remember you must have 24" in front of the toilet free of anything else. That "in front of the toilet" zone includes the entire width of the toilet zone, which starts at the center of the toilet and extends 15" to the left and to the right. So your sink cannot be in the area that a 2 ft long box, 30" wide sitting in front of your toilet would occupy. Neither can recessed wall cabinets. That imaginary 24 x 30 box goes to the ceiling I believe. A few of the small wall sinks available