Interesting design concept, I'm also working on a new hot end, since clogging, energy waste and assembly/disassembly issues are bugging me. However I'll stick to the cartridge heater.
I think one of the larger drawbacks of your proposal is the steel part which functions as heater and nozzle at the same time. I thought about an induction heated steel part that sits between your alu/PEEK pipe and a standard Ultimaker/Makergear brass nozzle. So you would just have to replace the brass nozzle when changing extrusion diameters, instead of the whole steel nozzle, which is probably more complex and