You have a two year old house. Unless you'd truly USE a tub? I would say NO. Least expensive is an improvement to the chill issue, and a nice upgrade to materials with the fewest moves to plumbing. Basically? Add glass and then what you want to style.OR.......... rip the whole right knee wall of shower entirely, and make the entire shower glass. OR........... lose the bath entry to the linen closet, open it to the hallway instead. Extend the vanity.......ignore the numbers there. 39 x 72 shower, 47 inches path in front of vanity, and 22 for vanity . With little major plumbing changes. Just the loss of the linen. Much depends on WHERE you want the space, and how you store bath items. And the budget. But............you don't have great space for decent shower by today's standards AND a tub that many do not use. At all. or...................

It doesn't make sense to spend the money for new countertops and everything to be installed on them without changing out those 40 year old cabinets. You can also get better function with a new design - different drawers and maybe an inch or two taller? You want your new bathroom to last. Mirrors like that can't be repaired, but it's not that expensive to get new ones. That also gives you the opportunity to use a taller back splash, whether you choose tiles or a self backsplash with the countertop material.

Please post proper pics not the fish eye ones and black, white, brown and gray not exactly making my heart go pitter patter for decor. IMO keep it simple forget the colored lights IMO your inspo pic is awesome stick with that look and you will not go wrong. Same color floor as shower walls and honestly unless you are doing a black sink , toilet and tub I would return those black fixtures and go silver . nice high gloss white vanity with a white and gray marble top , timeless and beautiful spa like space .

Given both those changes, an experienced designer would be a good addition to the project. You can, however ask for design help here in a new thread. You must include a diagram of that area of the house that includes the neighboring rooms, has measurements for every wall, window, and door, and shows placement of electrical and plumbing. You will get a lot of ideas and suggestions. Are you keeping the bidet? Will you consider moving the toilet? What is below this bathroom (ie: basement, crawl space, lower floor of multi-storey home)?