I have had a vehicle designed for my 15mm control battalion and it has a swappable rear compartment which can either be a tank insert (large beam cannon on a cherrypicker arm)...
(Cannon and arm not shown)
Or an apc insert with a passenger compartment ...
Here’s how it looks with no rear insert:
It’s very easy to just magnetize it and swap out the rear compartment. So would you want to buy ALL parts in one kit, for more money, or just buy the parts for one version only, but less expensive?