Userstyles only work client-side and generally per-site (I use userstyles and created some).
If someone would like to suggest improvements to the overall appearance of Discourse, any suggestion can be made in #ux, and if nobody creates a theme component or include wanted changes in Discourse, any user can make his own solution I guess. Whether it’s a theme component if they’re admin or a client-side solution if they’re not, with their own CSS from whatever browser plugin floats their boat.
But then, this is not really a Discourse-oriented discussion anymore I guess.
@GVG take a look at this related discussion, it could be interesting to you: