[gf000]

You only need a single implementation that exposes an API for running a WM as an extension.

I don't really get why would it be a good idea to somehow mandate a specific architecture design from the standard.

[nine_k]

We need a compositor that exposes everything as an extension. Preferably in a hot-reloadable, tweakable way, say, using Lua (with JIT). And also exposing its APIs in a way that allows having an analog of xdotool.