Christopher, by the way, why are you creating a new uniform, or even a single Starfleet, directly after the Federation's founding? Correct me if I am wrong, but doesn't the Mirror Universe and to a lesser extent the story 'A Less Perfect Union' actually show that the TOS-era Starfleet was a successor to/extention of the Earth Starfleet (although it could be the Chicken and the Egg scenario).
Obviously Earth Starfleet is one of its primary antecedents, but it doesn't make sense that it would be the only one. It's not like the other members' space fleets/services would've just evaporated. As I said in my initial post, they may have made greater contributions to the Federation Starfleet than is superficially apparent.
The Mirror Universe's 23rd-century ships presumably looked the way they did because they were copying the Defiant
's technology. As for the ALPU timeline, we couldn't actually see
the ships, so there could've been differences in the tech that weren't evident on the page.
Besides, why not make a change? This is the start of a new era in Trek history. I'm not just doing more ENT, I'm showing the beginnings of the institutions we got to know in TOS and beyond. This is called Rise of the Federation
, after all. The new uniforms are symbolic of a new beginning, both in-story and metatextually.
Not to mention that changing uniforms is kind of a Starfleet tradition. Kirk's crew went through four different uniform designs in 20 years -- pilot, TOS, TMP, and TWOK. Picard's crew has been through almost as many in a comparable span of time -- TNG seasons 1-2, the slight variant design from seasons 3-7, the DS9 fatigues used in GEN, and the FC-style uniforms. Archer and crew wore the same basic uniforms for a decade -- I say they're due for a change.
As for the timing, the Starfleet Academy seal introduced in TNG specifies a founding date of 2161, so I'm kind of locked in there. But that doesn't mean there isn't a process of transition and evolution to be explored.