We might be getting a bit off-topic with this ship stuff.
But personally I wonder how much of a big ship Steele would need to fit everyone in?
The starter ship has 3 bunks, including one for Steele themselves. The first upgrade might still not have enough spaces for everyone we can currently recruit. We have (and I may be missing some people here) Anno, Azra, Bess/Ben, Celise, Kase, Reaha, Sera, Pippa, Yammi & the Pexiga, and the goo armour and Siegwulfe.
As noted above some of those might not need full quarters, including the goo armour, Seigwulfe, the Pexiga, and Celise. Though I think Celise at least would need some space to store her belongings, even she doesn't need any room herself. (And it's just polite to give her her own room.)
That's still nine rooms, including one for Steele.
And some people have increased space needs, also noted above, such as Azra's plant collection and Yammi keeping the Pexiga somewhere.
If the Casstech is the size of a shuttle, you'd probably need a Millenium Falcon-sized ship to store all the crew we currently have in individual rooms (which is what most of the current text assumes) rather than bunks. If you converted at least some of the cargo space into more rooms. This would, of course, depend on how big the individual rooms are and how much space you wanted to dedicate to other uses (cockpit, cargo hold, engines, power core/generator, weapons & shields, communications & sensors & navigation, life support, workshop, other engineering doodads, galley, bathroom equivalent, other common areas, medical bay, entryway & access corridors).
I don't know how much the size of the rooms is mentioned in content, other than everyone having a bed and Azra keeping her collection somewhere. So I guess the rooms might not be much larger than a bed and maybe a desk and some place to store personal belongings.