Starfleet essentially did appoint a supervisor to Sisko. After a variety of Admirals from nearby starbases had given Sisko direct orders, he got a permanent big brother from Admiral Ross. It's just that Starfleet dared not station this supervisor aboard DS9, as this would have tipped off the Bajorans to the fact that their Emissary was just a pawn in a bigger game. (Okay, no need for "tipping off" - Bajorans aren't stupid. "Rubbing in the face" was the expression I was looking for.)
It would explicitly be different from other Starfleet missions, at it would evolve organically with the situation, thus be sui generis.
Which may well be what separates a "deep space station" from a "starbase" in practice! If you call it a "starbase", you have to stick to certain rules. If you choose another name, you have more leeway for opportunism.