@alan_g said in Mir 1.x and beyond:
Mir doesn’t (yet) have a clean API for adding Wayland protocol extensions in a server and, in any case, those that are needed by Ubuntu Touch are simply exposing existing Mir functionality. So, once the necessary protocol extensions are identified, the Mir code is the place to implement them.
Small clarification, that was a year ago. There's now a way to add Wayland extensions to Mir servers.