My suggestion is also a 'role bay'. An area that can quickly be reconfigured to take a crate/pallet of auxillary equipment that can adapt the role of the aircraft quickly. When not in use the role bay could be fitted with Pax seats or a small rest area with a couple of bunks.
In addition make the aircraft maintainer friendly for example trim that is easy to remove and refit.
O2 on tap for all to alleviate the Kokinelli headaches.