Likely one of the reasons a vertical EDZ isn't done is because folks on 11 meters haven't been homebrewers to the extent that Hams have been, and for all practical purposes wire antennas have been horizontally oriented in the Ham community almost exclusively.
I do imagine the large matching system on the EDZ has made it impractical, too.
I think the self supporting vertical is not a big problem provided the matching network can be reduced in size and mounted in a practical way. As my thoughts have been so far, should the matcher I use with the EFHW be usable it is done.
5/8 wave aluminum tubing straight up from center insulator, 5/8 wave tubing straight down. Coax up through the bottom tube to the center insulator, and the matcher mounted there feeding the two ends. The whole thing would be VERY long, and that alone makes it a doubtful project in terms of value to logistics ratio, but doable.
This match handles the kind of impedance mismatch associated with the EDZ with ease.
As for your idea on the double bars curled around, I have pondered such a thing for other applications than an EDZ. I thought more in terms of a Beta Match at the center of a 5/8 wave dipole similar to the gainmaster replacing the capacitor/stub match inside the GM. If workable it would certainly end the discussion on power handling that has been an enduring subject for that antenna, and simplify homebrewing possibilities for we simple types - if you don't mind ugly.
