I have to echo the opinion that the crew is a bit too
diverse, and containing too many unique species to maintain the suspension of disbelief.
Also, nobody makes Commodore by 38. The ages of your senior officers are all too young, leading me to believe the author is in his teens or early 20's. To someone that age, 40 is ancient.
It is, however, the age that people in actual military forces start reaching the age of Captain/Colonel/etc.
Also, it's Starfleet.
One word. No space. No capital 'F'. Starfleet.
I do think the premise has promise though... hey, that rhymes!