It would be neat if there were userspace Miracast framebuffers. Could have a larger number of information displays around and just send images to them occasionally without having to have run X for each, or whatever.
If I understand your goal correctly, would EVDI (Extensible Virtual Display Interface) not be a possibility for you?
EVDI allows to create "virtual heads", that you could then conceivably cast to external displays via `miraclecast`, VNC, etc.
It was originally created to support some ancient USB graphics card, but can be used independently off any specific hardware.