After looking around on thee internet I came up with this rough sketch and went down to the local model shop to procure some styrene section and sheet....
The transporter (I'm yet to think of a name for it) will be unarmed but will have the option to mount a heavy stubber in the turret above the cab. I thought a transport capacity of 20 with armour values of 10/9/9 would do the trick. I need to have a play with the Vehicle Design Rules soonish. With a transport capacity of 20, three vehicles should be able to manage a (maxed) IG platoon with a support squad which seems a fairly realistic. Imagine three of these in convoy taking urgently needed reinforcements to the front.
I have so far fabricated three chassis, so now for the hard part of doing the cabs and body work. I was stumped over what to do about wheels for a while until it struck me that LEGO makes nice chunky 40kesque truck wheels, twelve of which I procured from these friendly people for a few quid.
Well here's the work in progress, I'll hopefully have something looking truck like soon.