Not sure having shared memory and socket open to N fresh and under active feature development c codebases is that much more conducive to security? (N since while many compositors use wlroots there is still enough rope to hang yourself). To be fair, unless there is a exploitable bug in wlroots/lower wayland code, the blast-radius will be a lot more limited than if one is found in Xserver.

I think the Qubes approach is the only one worth considering if one deeply cares about security.