That actually already exists. In fact, it's how you're able to graphically admin an XMPP server from any common XMPP client, as the server just presents a different form for each type of operation: https://xmpp.org/extensions/xep-0004.html Thus as features are added to a server, it's only a server-side change, meanwhile nothing in the client has to be updated to admin new things, since it's just a basic form syntax to express it.
FOSS spergs won’t take this seriously because they think the debate ends literally the instant you bring up that their alternative is FOSS or that it has E2EE.