In regards to the "accidental" crew the easy fix would have been for the alien that visits earth to simply kidnap a (seemingly) random selection and fire them off to its home planet in a secondary ship.
I was thinking more along the lines that this was the only ship available on short notice - basically come up with some excuse that all other FTL ships were out of comms range in deep space, and they didn't have the time/energy to swap out the existing crew, so they just decided to put Niko on top of the existing command structure.
But it still makes no fucking sense. I mean, the series makes it clear that FTL drives have been around long enough in-universe that it's not seen as a big thing. Presumably this crew has had experience going to other star systems - because what the hell else would they have been doing? Yet they ooh and ahh when they land on a rogue planet as if no one has ever done it before.
The worldbuilding on the show is paper-thin in general, which is easiest to see when you look at the Earthside scenes. Everyone dresses just like today, talks just like today, tech isn't that different from what we're used to except for a few doodads, etc. Yet due to things like the existence of the FTL drive and discussion about rising sea levels, you can understand this isn't meant to be a near-future show. If they didn't have the budget to pull off a convincing "future Earth" setting they should have just cut the Earthside plot entirely.