Perhaps all the major member states have their own shipyards, but build from the same designs? That could explain why ships are crewed by mostly one species, like the Enterprise with only one confirmed Vulcan and Andorian, as well as the ships with purely Vulcan crews. In my little universe, USS stands for Unified Starfleet Ship, with ships built by various members but placed under a unified command structure. Originally the Federation kept the various member state fleets in service, since they were undoubtedly composed of many ships built for the Romulan war, but as they wore out they were replaced with standardized designs, like the Constitution and the Surya. The Daedalus was a joint project incorporating technologies from all the allies, which is why it is so different from earlier Earth ships according to The Starfleet Museum.
Given the depiction of Vulcan, the U.N. analogy is actually necessary. It at least was not fully incorporated into the same government as Earth.
Since the Enterprise's deflector is only orange/gold when it is powered down while in port, blue makes more sense. What if you made the hull more white with the highlights grey/silver?
I have come to dislike the huge deflector dish. It doesn't make sense that it is necessary for Federation explorers or heavy cruisers but not for any other ships, Federation or otherwise. I'm beginning to wish Jefferies had made a much smaller dish with other structures on the end of the hull to make it interesting, like a big hatch, an observation deck, or maybe the torpedo launchers.