The bit that concerns me, especially in light of flyby's comments, is that when one wishes to overfly the circuit, have a gander at the windsock, and then choose a runway for landing, this is supposed to be at 1500' - to keep a 500 foot buffer between you, and traffic already in the circuit.
So what happens if a 1000' circuit aircraft trundles in, after having broadcast intentions to overfly, and having copied down the inbound regional turboprop joining downwind, yet assuming that their downwind is the same altitude as its downwind, both aware of the presence of the other, but unaware they are at the same height?