Definitely a lot of interesting paths to explore...and I'd agree that the one that's kinda front and center (Wendy and the pet Xenos) is kinda the least interesting. But lots of potential.In terms of spin off potential, its actually been a very good series, I for one would watch a spin off series of Morrow (prequel maybe) and I would happily watch a spinoff series of Kirsh (prequel maybe) , I'd also happily watch a spin off prequel series of the founding of Prodigy to see more Atom Eins. I would also happily watch a spin off series of the original ship capturing all the different aliens on the different planets. On top of that I'd happily watch a spin off series of the eyeball.
So thats 5 potential spin off shows that I'd be happy to watch. Bunch of possibilities there, as a foundation for an Alien Earth "universe" its been very effective.
The main story arc with the synth kids and are they/aren't they human is solid I think, I'm just not wild about the pet Xeno stuff. It's never really been explained why she can communicate with them.