A bit of a problem. I'd do it for a short trip across town, or if my controller failed but not a long planned trip. I haven't got a controlller in my ute yet and should borrow the Mrs' car to tow. She's not keen on using the ute!
Surely there is a market for a wireless controller. Something you could connect inline with the trailer plug, on the trailer, and use a wireless controller in the cab. would mean you could buy one controller for the trailer and switch it between tugs in a few seconds.