I did have a colleague a while back who had a Seat Alhambra (same as the Mk1 Sharan/Galaxy) which had a 3 bike rack that attached directly to the tailgate, I don’t think there was any drilling or straps involved it simply clamped on at four points around the edge of the tailgate and he could still access the boot and use his tow ball for towing, I think it also held the bikes a bit higher so the lights and number plate were visible (obviously without a trailer) and he didn’t need an extra light/Reg board…
It was a pretty sweet setup, He pretty much left the rack on all the time… I’m buggered if I can remember the make of that rack but I’m sure some googling would turn it up…
Keep the Roof empty in case you want to use a roof box, or to go on a ferry…