Is this possible now? I can't see why not-put an mtb cage on a 9070 derailleur and a looong b screw. Maybe the cog spacing is different, I don't know.

Besides the ridiculous cost, it seems like the future. I kind of doubt sram will go electric, or shimano 1x11, soon, but maybe when ultegra goes 11 speed electric and XO is 1x11 next year it won't be THAT expensive to put something together.