A Human Starfleet, a mere Trade Federation
A Vulcan scout ship suffers a minor mechanical failure, and as a result doesn't notice that humans have developed warp drive. As a result, humans leap into space exploration without having a truly unified earth, and when they finally do meet the Vulcans, their influence is much less potent on Earth culture. As a result, the "Federation" proper never really forms, and Starfleet remains a Terran organization, allied with the Andorian Defense Forces, and other planetary militias. After a war with the Romulans that goes badly for both sides, with a narrow victory for the Terrans, a loose "Trade Federation" is organized, but you never end up with the truly grand Starfleet as we know it - technology is more fragmented, with particular races having more or less of an edge in certain areas, and the lack of co-ventures in the areas of science and engineering are quite visible. You could play with this however you want, but I bet it'd be neat for the characters, on their way through this dimension, to introduce the seed of a multi-planet Federation with a unified government etc...
The Doc
Becoming Your Worst Enemy
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