What about a derailleur hanger with a hole that the skewer goes through so that it becomes a sort of sliding dropout. As you move the wheel back, the derailleur moves back by the same amount. Punctures would be a faff but not too bad. My 3T drops its rear mech when you remove the wheel, you get used to it.
What about a derailleur hanger with a hole that the skewer goes through so that it becomes a sort of sliding dropout. As you move the wheel back, the derailleur moves back by the same amount. Punctures would be a faff but not too bad. My 3T drops its rear mech when you remove the wheel, you get used to it.