Bike axle block/reverse chain tug?
Nearly all mountain bikes from early 1990's to early 2010s (which is 2 decades) and even now many low cost bikes, use Hollow axle QR on an open dropout without any concern. Sure the opening faces down, but many MTB's spend plenty of time with wheels in the air.....  

When pedaling the wheel is pulled forward with extreme force. When not pedaling, the action on the axle moves to a very small upward pull (depending on the derailleur angle). The QR would have to be extremely loose for the wheel to drop out. 

Is it a concern - for a manufacturer of frames intended to run as you desire, the lawyers would be insisting on lawyer lugs to protect against liability when someone does not do up the QR. However, if the QR is done up, its not a concern at all.