If I was going to have a mobile plant, I would be looking into cavitation processing. Not really tried and tested yet mind, at least not be us. Depends whether you want the hassle of building and testing it I suppose.
If your talking about and old Transit, pre 2000, smiley face, You do know that they will run on straight veg, don't you?
Certainly your options on what oil you can use increase dramatically when making bio, but then they do with a heated tank aswell, which would be very simple compared to a mobile processor.