I have no QR mounted hitches. I built a rear straight-pull hitch for my cargo bike. Two kids trailers connect to the chain stay, and 1 to both the chainstay and seat stay. The Bike Friday trailer has a special air hose connector permanently mounted to the bike.

However, in your case, If you have access to rudimentary welding and machining, there are two solutions I can think of.

1) Replicate a similar mount to yours with a small, but thick upper "washer" cut to the size of the dropout for a tight fit, and then attached to a piece of pipe for the hitch. If you wanted to use your QR as a "through bolt" type release, you could even permanently weld the new hitch to the frame.

2) Weld a short piece of matching pipe to the rear support triangle. Even perhaps welding your existing hitch, or a new replacement one. This would require a frame mod, but it would keep the hitch away from your QR.