I get the impression that one is able to create multiple uniforms and switch between them without having to pay for them multiple times; this feature is either unimplemented or has an obtuse means of use.

Would it be possible to have this explained?

I believe I got an extra costume slot when I hit commander in beta, you also might get another at Admiral. That's the way it worked in CoH too. One costume til the mid levels or so when you got a second one, then another at the end levels.

Plus one when in a Fleet.

My toon bio states she is a shape shifting alien thanks to the uniform switching. Not only can I set up a second uniform but I can set up a completely different alien as well. Slot 1 is my normal lil green alien and slot 2 is when she shape shifts into a human woman. If a third slots unlocks later I'm totally making her a klingon alien too. Really opens up role playing switching from alien to human (looks human but still says alien of course) on the fly.