Fookin AWESOME idea.
And definately do 2 rooms 1 for veg 1 for flower (be easier to blackout aswell if its a bit smaller)
The only thing you'd have to worry about is where will the smell drift to??
Cos if you put a filter system in theres gonna be noise and possible drifting.
(unless you could put 2 filters in each room to disperse the smell somewhat, i suppose it depends how close your neighbours are).

hope you go for it cos i'd love to see some pics of that..
Us here in uk couldnt do that we dont have big enough driveways let alone anything else.

P.S security for your van would be an issue maybe have locks on both rooms aswell as the main van.

GOOD LUCK!!!!!!!!!!!!!!!!!!!!!!!!!!!!1:hippy: FLOWER POWER RULZ