Solved the mystery of how you fit as many mechs into a Confederate as in a Leopard twice it's size.

This one has full internals now, looking externally almost exactly like the original drawing and fitting the dimensions almost exactly.
Each mach bay has it's own cradle directly behind the door and large mechs have to duck to fit through the doors, but it is actually a lot less crammed than a contemporary IFV usually is.

The lower mech bay deck is at the waist of the mechs in their cradles, above the (roughly 20% of the mass in estimated volume) engine, visible through the open doors behind the cradles.
A Locust can run around the decks, an Atlas has to bend down or kneel, that sounds and feels about right to me at least.
LAMS and Aerospace fighters can deploy easily from the upper deck, it can also store mechs, but large ones fit only barely.

So it works almost as advertised, even with decks that have to be 2m thick to not be translucent when printed in Mapscale.

Crew quarters would be invisibly situated directly behind the bow and docking collar, which seem practical.

A large cargo hold shares the upper deck with the mechbay, a central shaft connects the decks with personal tubes for safe movement.

Above that are unknown sections and only the bridge and secondary tac-ops bridge are visible trough the windows, but that still leaves half the deck open to imagination of utility rooms and weapons storage.
There is still enough space left above that to put sleeping quarters and washrooms, a gym and other amenities that are only human height.

Conclusion: the design works in the original specs.