Hey mate, this has been an interesting read and hope I can help out. I put a Kaymar on mine and carry a second spare there and agree weight is a big issue especially when towing. It is very very easy to get the dual cabs past there GVM especially with a trailer on board so make sure you know your weights of the car loaded, the van loaded, then combined and ball weight. I know my truck partially loaded (no beer) with me and the mrs is 3.1T, then add my FF camper (2T GVM) with loaded and measured 190kg ball weight I am over the factory vehicle GVM, lucky I did the OME GVM upgrade on purchase.
My advice would be the following:
1. Carry the second spare on the trailer - underneath if room around water tanks, perhaps look at a different profile tyre to reduce the clearance impact (how often will you actually use it)
2. Change the wheels/tyres on the van to match the profile on either 16" or 17" rims, the van looks like a zero offset rim (standard BT is +55) so in an emergency will get you out of trouble with a bit of wheel poke out the guard, easiest option. Also if you carry a hub adaptor can use the BT spare on the trailer if you blow 2 on that, food for thought
3. Carry it in tub against the front if you have the room
Changing the tyre is not that hard after a bit of practice, however in the desert can be a real bastard on a hot sunny day that has already gone wrong....