I think it would be perfectly fine, and probably better, to make an entirely new thread for this.
A personal opinion that I have expressed elsewhere is that I think we should avoid adding specifically humans. Among other things, we don’t know if what we end up with for 3D editor can make humans that don’t look weird.
I would prefer we have something that is clearly a stand-in for humans but also not entirely human. Compare it with Kerbals for example. (I would also like the their species’ “story” to be one of the potential selections for if you start in a later Stage)
I think you might be reading into the Space Stage a little too much as a Stellaris equivalent. I could be wrong, but this seems like an overly specific design that makes sense as a Stellaris-style non-player crisis, but not as something that arises naturally from the normal Thrive game mechanics.