Dunno… a sturdy topping lift is what you need if you ever need to use boom & mainsheet as a crane - to lift a MOB, outboard motor, or the engine, for example. And I’ve seen a few boats at anchor for a week that use it to lift the boom clear up out of the cockpit.
Also, I figure the 3:1 vang with snap shackles is my emergency block and tackle to fit between the halyard and LifeSling if that ever has to be deployed.
But yeah, going down wind without a vang is just an exercise in futility. I suppose this is most obvious with end-boom sheeting. At some boat size, a rigid vang with hydraulics becomes de rigueur, as the forces become to great for rope tackle. Not sure what size that is… >40 ft-ish?