Youd be suprised at what you can fit in the back of a OLD Tarago or the like (dont know about the egg shape ones and they are too dear anyway).
They tend to be cheaper than the "proper" cargo vans (nearly as cheap as a dedicated bike trailer), the seats come out easy enough to, they have a VERY low loading height and the added bonus of glass (to see when driving but also lets the crims see in

) and you can just lock all your gear in too. You CAN squeeze two bikes in but a takes a bit of jiggling around (the bikes you fools

). Some even came with 2 litre motors and I have been busted for speeding several times on the way to and from trackies in the barstard
I have fitted the ZX7R and Ducati Darmah in the back but had to take the screen off the ZX12r to fit it in. Just bolt two or three tie down points in and off ya go. Where the seats clip in at the back makes a great tied down point for the rear. When you are finished, put the seats back in and sell on but they may wonder what all the oil in the back is.
Just beware the rack and pinion, it costs a mint to repair.