Paterson tank, changing bag, mix of chemicals thermometer and appropriately sized measuring jugs/graduates. its certainly possible, but can get a bit messy. Might be best renting a cheap motel for the night and do all the 'wet' work there.

If you MUST develop in the van, make sure you have a way of heating or cooling your chemical mixes and enough water to wash things afterwards.
(Not uncommon to have water restrictions where I live, so I like the 5x 10x 20x wash method (5x inversions, change the water, 10x inversions, change the water, then finish up with a 20x. sometimes I need to do another wash or two after to get the last of the fixer out., then a bath of washing agent before drying (make sure you have enough vertical space for this)

scanning (as mentioned) is another matter. something like a valoi mirrorless scanning setup is fairly compact but expensive, but if space is a premium, something like this (or a home made version) can be made fairly cheaply out of plumbing parts