Have some free time and some metalworking skills? I have neither. I think there would be some demand for making something like this that would fit on a tapped simplex hanger to run a standard derailleur. Preserve the French hangers, non-permanent modifications, etc.



I know this is an option but how could one sleep at night?

Non tabbed drop outs have had various mods to handle a der mount that depends on a tab. A common method is to drill and thread in a small set screw into the hanger's perimeter at the same rotational location as a tab is. Then this screw sticking out acts as said tab. This is as old as the hills. The drop out in the photo would need some grinding away which will create a tab, also a time honored method. Andy

Tap the hole and track down a shimano crane, that's my favourite option.