What you want at that point is to agree where to read and write common configuration. I'm not sure this is likely to happen either, as gnome has gsettings/dconf and kde has simple files and you will now awaken the plaintext vs efficiency dragon.
The current situation is just how it coincidentally turned out - there's just not always a clear direction on the free desktop (and that's even what many people like about it). If wlroots or something similar had existed earlier, then this probably would have turned out differently but c'est la vie.
edit: looks like it might already be provided via wl_output::scale [1] except you get the wrong effect that way. You want to tell the client what DPI they should render at, so that you can keep scaling at = 1
[1]: https://wayland.freedesktop.org/docs/html/apa.html#protocol-...
This is not something conceptual about Wayland, or intrinsic to it. Any display protocol can have multiple client/server implementations. It just so happens that most of the free desktop standardized around the X.org implementation for X11, but even for X11 there were multiple client and server implementations.
The second thing is that software duplication efforts have a well known, tried and tested solution: implement the duplicated effort in shared implementations or libraries [1] !
The thing I find hard to wrap my head around is that this complaint is given in a community that usually champions protocol-over-implementations and diversity of implementations. The people actually making a difference on the Linux desktop are damned if they do and they're damned if they don't.
[1]: https://github.com/swaywm/wlroots