Accessibility and the graphics stack

Again, shortcut handling belongs at a higher level than raw keyboard layout handling. This has to account for things like negotiation between global and local shortcuts (e.g. when the media keys such as Play are pressed, who handles it? if the foreground application, then use that, else try to find a backgrounded media player?).

The shortcut handling itself is also intensely difficult - for instance, when you have mixed layouts such as Russian and US, you want to base the shortcuts on the US layout, but then you can throw in mixed Dvorak/US for fun.

It's not that this isn't supported, but just that it's the wrong level to support it. The kernel doesn't deal with keymaps at all and just forwards on keycodes at all; the window system doesn't, at its lowest/fundamental level, deal with shortcuts or locales either.

Nothing in Wayland precludes this from being built on top, at all; in fact, it was designed with the explicit intent of being able to do so.