Apart from the headache of the wiring that runs down each side of the roof my suggestion would be to raise the roof. There are a few example here on the forum. Alternatively a pop top such as Sportsmobile do but I would be concerned about the reduction in the rigidity of the module in the case of an ambulance. (It would still be better than a normal cannot an RV but not as good as the current cage structure)
Yep that adds a lot of $$ to the project, but something along the lines of HobieTony's roof would be awesome. Pricing on the above truck came in a little crazy....
Yeah the main reason on not drawing it out to the 45 is because there are usually cupboards down both sides anyway and it is a lot stronger. You could do a mix of both and trim it back to the 45 where you want the access such as the doorways and leave it at the 90 and build in storage above the cupboards.
That rig sounds like a good one but I bet it is spendy.
Ouch that's still in service money. Still a lot better than a Fuso but ouch.