I've always been a fan of the fact that in Star Trek Generations that the crew of Enterprise-D wore a mix of the TNG and DS9 uniforms - the Belfast-type interior seems to be a step in the right direction for this with NPCs wearing more than just the Antares-02 uniforms (which seem to be the primary Starfleet uniform of the 25th century judging by the NPCs wandering corridors of ships and starbases). Hopefully in the future the devs will allow us to make use of Blackavaar's uniform guides or our own uniform designs and implement them on those NPCs to make each interior less like a ship full of clones.
I was surprised this was not already an option when I first started playing, after playing City of Heroes (another Cryptic game) for so long, which had so many costume options.
I hope to see at least two or three sets added, but would be happy with one general crew standard uniform that you get to customize for your ship (one for each field service of course).
Bridge Officers should also get a second uniform also, and you should be able to earn more uniform variants, and not have to purchase all of them with C credits! Maybe at Captain and Vice Admiral or something you get additional costume slots for your BOffs and yourself.