Unless you are a licensed and trained architect, you should not be designing anything. The issue is your professional contractor is trying to build amateur plans. You really need to hire an architect to design this addition, and then if you really do need metal beams, you need to find a contractor that knows how to work with them.

Unless it's an illusion, there are shadow lines that make it look like the floor is dropped for curbless. Talk to the builder about the curbless. Make sure they include a capillary break on the floor at the shower entry/threshold. Ask specifics about waterproofing, how the walls will be built out from stud to tile. Shower heads, it's a good idea to not have them spray directly at a door. Because of that, I'd recommend you consider having a shower head on each end wall. One can be a fixed head, the other a handheld. Make the handheld hose long enough so it can be used to wash down the shower as needed, yet not so long that when it's on the bracket the hose is scraping on the floor. Shower door swing, consider a door that will swing in and out of the shower. Bench? Consider a moveable wood stool. You can place it on an end wall, or on the long wall, or take it out of the shower as needed. Should there ever be a need for home health care, the aide will much prefer bathing someone sitting on a moveable chair versus a built in bench. Built in benches are sound great at first blush, but in reality they are a shower disaster waiting to happen. Good luck with your house build.

@thinksesignlive...that’s a great image. Do you think the wood slab ceiling would make the space darker further and make the ceiling feel even lower? What do you think if the wood seat ceiling had slats of mirror randomly incorporated in the space? Then on the floor which which could be wood slat as well, but incorporate random pieces of a heavy duty frosted glass (the feel of a water element) in the space. Instead of a couch for entertaining guests, incorporate outdoor patio furniture but more lush but durable cushions (sunbrella fabric). Maybe just a couple tall low level light plants, use a plant service to change them out every couple months. Lastly, add a simple zen water feature so block road noise and bounce light off of in the evenings. Movement in a space adds life to it,

If more pictures are needed please let me know. Or if anyone can share what ap there is to see real furniture in their room that i see people use on here would be greatly appreciated. Any tips are welcomed !!