It's generally a bad idea to do it that way. I think I'm just going to rewire it and keep it simple. The only issue is how to hide the relatively ugly cable. Will probably use a Wiremold tube along the wall, and use a cap at the top to feed the flex. I also may just use 1/2" flex because I have 250 feet laying around collecting dust (what? it was $40).
It's generally a bad idea to do it that way. I think I'm just going to rewire it and keep it simple.
Hey, I never said it was ideal. I'm looking at safety and code compliance. A disconnect with properly sized overcurrent protection will do that. The picture you posted would be sufficient. It doesn't have to be fancy.
However, if it was me I would bring a #14 back to the panel. Yeah it will be a major pain, and yeah it will take time, but you'll feel better when it's done.
Just remember you will need to put in a junction box to tie the old feed and the new return together. There won't be enough room to make a connection in the existing device box. --