Well Canis Wolfborn rides one and he's on a 60mm base.
Space flights are launched from the Earth at bases, from launch pads.
A [right] cylinder
rectangle
Circle
cylinder
It is a cylinder.
Cylinder
It's the biggest continental state. More space to build bases = Bigger bases. Bigger is better.
A cylinder would fit the given description
No, the only Warhammer 40k vehicles that have bases are skimmers.
A triangular prism.
It forbid weapons of mass destruction in space and doing things like testing such weapons on the Moon or building military bases there.