I don't think hub motors are a good idea in general. Dirt and debris tend to get stuck in the bearings. There's a reason that hub motors aren't in any production EVs.No problem, just throw in 2 rear hub motors like these and attach an appropriate battery.
Peak power of 30 kW provides sufficient acceleration, and with 15 kW permanent you should be able to go almost 50 mph.
No gearbox or clutch needed
Loads of people have converted VW Buses which are very similar vehicles. I'd recommend looking into what those people have done. A used DC motor and some batteries pulled from a Nissan leaf would probably be the way to go.