We remodeled (a smaller house than yours) and moved laundry to upstairs. We don't have a dedicated laundry room (didn't have one before either). But, we have more than a stackable-size only closet for laundry. My laundry closet that is convenient to bedrooms is 3 1/2 feet deep by about 9 feet long with 8' of bifolding doors that make the "closet" open into a room-size when those doors are open to the hallway. It feels room-like to me. And, there is plenty of room for utility type stuff--a counter top, space to put the laundry baskets, laundry detergent, etc. What you show in those images, I see no practical space for laundry detergent, hang-drying, etc. So, does it need to be a dedicated room? No. But, more space than a tower closet for a family house (2900sq ft is larger than my family sized house).

You can't just "flip over" the lever handle will point in a different direction ( up/down) . My advice is show the builder what you want, and let him ORDER ALL OF IT. Hinges, rosettes, handles, should all match. btw

@Jack D - Yes, like that, but can you move the W/D to the opposite wall that it is currently on and reframe the doorway closer to the "new bedroom" (might need a pocket door to laundry) perhaps shrink the laundry room a foot or whatever you can get making a bit more room for the closet system? I don't like the open closet system as I prefer the ones with doors. As a designer and a realtor, even though the room is small, you still have the extra room. I've got 5 bedrooms in my home and one of them is only 10 x 10. I've got a twin bed in there as well as a dresser. It's my sister's favorite room to stay in when she visits. https://www.ikea.com/us/en/p/pax-wardrobe-white-bergsbo-white-s19127297/?gclid=Cj0KCQiAkePyBRCEARIsAMy5ScuNAD-dsyPBUR5RMtwyJY550Nz6nsSDgCNi8biKdAOBwSi8dWbarqoaAr-8EALw_wcB

I agree about bifold doors...if not necessarily flimsy, they are awkward to operate and don't fold out of the way enough in many applications. I love your idea of the partially sliding in doors and would pick that solution myself. I don't think you need louvered doors either, they are a pain to keep clean and what kind of ventilation does a washer/dryer need? None. I'm not sure if any of the previous links go to this source, but they have a great selection for what you want, up to 110 lbs: https://www.richelieu.com/us/en/category/sliding-system-solutions/sliding-solutions-for-cabinet-and-furniture-applications/hawa-concepta-series-pivot-and-slide-in-pocket-door-system/1206997?nf_1031396=%281764651%29