Some interesting takes on uniforms, there. I like how they keep the TNG feel throughout.
My main dislike would be the excessive number of 'fancy' variants. I don't see any reason why you need a dress uniform, then also mess dress and dress whites. It's kind of silly now and seems even more so in Trek, even with replicators taken into account. It seems like either a uniform is formal or it's not, there's no need to have formal, extra formal, and super-extra formal, especially in the main differences are just a little extra glitter (in a society that doesn't place extra value on silver or gold) or a couple extra stripes.
I thought the same thing. The real-world trend has definitely been toward practicality and simplification. WW1 was kind of the high point for "fancy" uniforms; by the time WW2 ended US Navy officers' service dress blues and whites -- ordinary, everyday duty wear before the war -- were as formal as things got, though mess jackets did come back, optionally, in the '50s. The way I see it, three uniforms should do it: dress, duty, and field/working/utility.
Modern materials have made summer-weight uniforms more practical, there's not really a need for lighter-colored uniforms for warm weather anymore. The US Army, Marines and Air Force have all dropped their khaki/tan service and white dress uniforms. The navy will probably hang on to its dress whites for the foreseeable future, but I don't really see Starfleet as needing a white variation.
That is also the reason, I really like wat they did with the uniforms in TMP, where there seems to be quite a bit of freedom when it comes to "dresscode" for the crew. But I´m aware I may be rather alone with liking that
No, you're not alone. Conceptually, the TMP uniforms were the strongest in all Trek.
One other thing I was looking through was ratings/MOS. We have engineer's mate, yeoman, etc., which in modern Navies have insignia. Where would that be indicated on this uniform, if anywhere? On the shoulder stripe? Or perhaps only on dress uniforms like the sleeve rank pins of the Wrath of Khan era?
It's hard for me to picture since Star Trek did without that sort of thing for so long. The real-world trend is away from that, too. In the US Navy, with the demise of enlisted summer white, that actual rating badges with specialty are now only seen on dress uniforms, and the peacoat. But the upper sleeve would be traditional.
ETA:
A related question would be - what are the ratings for people like the CMO, Chief Engineer, First Officer, etc.? Those are positions in and of themselves, rather than something you really train for. Is it possible your First officer's rating is "Quartermaster's Mate" or something else? How's that work in the US Navy?
Enlisted personnel -- petty officers -- have ratings, officers do not. On a USN ship, most of the departments are run by line officers, who are trained to, eventually, take command of ships. The exceptions are the supply department, run by a supply corps officer, and the medical department, run by a medical corps officer, who can't ever command a vessel.