I was going to suggest the same thing. I had a custom ti fix gear made and asked for a welded on hanger but we waited until I had ridden it a bit to see where that hanger could best be located for on-the-road wheel flips. The route we went (at the builder's suggestion) was a threaded hole through the dropout above the slot. I used a pan head SS bolt with a nut tighten against the dropout. Looks not too different from yours (except different location) and works really well. (I think I will get a flathead though based on what I see here.)

Best part of the threaded approach for me? When I got my hands on a 12t cog, it came with a special lock-ring since with a standard lockring, the chain would be riding on it, not the much smaller cog. But that lockring is a bell shaped piece that extends much further outboard that a standard one. And made real contact with my chain hanger. But with wrench and hex wrench and 2 minutes, problem solved for good! A thank you to the builder.

Ben