Great idea, Graham. I am dealing with this issue right now with my new BRS 15 mk2.
We took it for the first sail yesterday and when rigging down, were able to leave the sails lashed to the masts when laying the masts down. I disconnected the sprit tackle from the masts (snaps), and because of the way I installed the lashing, the sails naturally flaked with a little assistance. I was then able to roll the flaked sail, still lashed to the mast, from the clew up to the mast, then stuff each sail in its own sailbag. These bags then hung down into the hull, mostly, and travelled well at highway speeds. All lines still remained reaved through their blocks, except the sheets and snotter tackles are unsnapped from their sailing positions.
I still have the loose ends of lines to deal with, but experience should allow me to clean these up.