Hi Twang.
You got it right about the flappy side door, they can be a git to adjust and make water-tight.
Iveco – cheap, big, strong. Thinks its a truck. Can get a 5’11” bed if careful, I reckon you need an extra inch or so over your height to make it comfortable and not feel like the bed is too short. RWD = high floor.
Sprinter and Crafters = £££
Ducatos/Movano’s etc, probably a fairly good choice but built to a price.
Transits – big beam above the windows makes it difficult (impossible?) to get a reasonably wide bed at a height that gives a garage with a useable space (although I did see a pro-conversion recently where the windows were higher so they must have cut out a lot of the metalwork)
You need to decide if you are going to try and squeeze in a sideways bed, or a dinette that converts. A fixed longways bed will take up most of the space in a MWB.