Unless you get a 5th Wheel, you could still store things in an SUV.
A Van one would more than likely be even better , especially a Cargo Van.
One could also also add a Cap to a pickup & have storage in it.
As for turning a bunkhouse area into a Closet. I assume it would depend on the bunkhouse arrangement as to how feasible it would be.
But if you are going with a 5th Wheel, it would be a good option. Our son had a bunkhouse in a separate room. It would have been easy to use it as a Closet. The two bunks on one side could have been used to hang shirts & skirts, just by adding a couple of rods (& just take out the cushions/mattresses. For longer things a rod between the two sides between the bunks & the build in chest of drawers could have been used.