We could use primitive hulls as the basis.
You can't accelerate faster than factor/three, and can't install either manoeuvre or jump drives.
Considering the material involved, I'd discount plasma and rockets, as well.
It's possible that the prohibition against faster than factor/three, could be due to the lack of inertial compensation field, but that's not mentioned in the description, so I'll take it as presented.
The next aspect is what can you install inside the bladder covered superstructure, outside of the drives.