Re: the bulletpoint "Show preview of mobile to desktop editors", just a reminder that there's a proof-of-concept gadget at Enwiki that accomplishes this.
It can be tested with this link: https://en.wikipedia.org/wiki/Moon?withJS=MediaWiki:Gadget-mobile-sidebar.js
Or enable it ("Mobile sidebar preview") in your account at w:en:Special:Preferences#mw-prefsection-gadgets.