If I'm not mistaken KWin has access to the entire desktop content. If so, does that mean it might thus be able to act as a VNC server (using the VNC qpa for inspiration)? That'd be a really nifty feature even if a bit far from traditional WM functionality.
KWin will not add vnc support for security and stability reasons. Due to that I'm setting to WONTFIX. But there is experimental code for adding a protocol which allows to write a vnc server. This might land for 5.13.
Is there a better place to post these kind of wild ideas, where they might get *whelming reactions from the community? :) I can't judge how unstable this might make the WM - hardly when done right I'd hope (possibly with the compositor turned off). I'd be more concerned about performance, but then this does not need to be something intended to allow *concurrent* access from multiple hosts. FWIW, OS X has had a builtin remote desktop feature that's nothing but a VNC server, and it is in fact what inspired my suggestion. You have to enable it explicitly, and then set a password. I never got to try if multiple clients can connect, but as soon as a client connects a conspicuous icon appears in the menubar ("system tray"), with a menu under it that allows to disconnect the client in a click. I highly doubt Apple would have left this option in the consumer version of their OS (i.e. not only in OS X Server) if the security risks were really severe. AFAIAC the security risks are only slightly higher than for the SSH server we all run -- once your IP is exposed.
Let's put it like that: it's rather unlikely that you will have an idea I haven't thought about years ago. How to do VNC is something I spent quite some time thinking about years ago.
Here's one idea you clearly never got: how to avoid spewing insulting generalisations and other petty remarks ("I'll break it just because I can").
I have now been the maintainer of KWin for - I don't know - 6, 7 years. I don't remember a single case where a feature or idea was suggested which I hadn't thought about before. You can think it's a generalization or even arrogant, but that's how it is. For the specific topic on remote rendering I even blogged about it in 2015: https://blog.martin-graesslin.com/blog/2015/10/september-update-for-plasmas-wayland-porting/ Please also remember that this is a technical issue tracking, that English is not my native language and that I'm German which means I'm extremely direct.
In that case, please remember that I'm Dutch so English is a second language and I am even more direct (or can be as over 30y in international exchange have taught me a minimum of restraint).