Theoretically? When using loadiine logger and Smash mode, it logs the libraries loaded for the Wii U Menu when you exit to it, and they pipe most stuff like icons through the normal coreinit FS functions so if you could detect the ID that way, you could overwrite the Wii U Menu binary with your own or just add some patches, but that'd still require a bunch of reverse engineering. It'll get there eventually™ but as of now it's still way too complicated
I also don't know if you can also overwrite the HOME menu, that'd probably be even trickier