A similar system as developed at my old unit.Due to the large amount of VFR traffic below 2000ft,the Radar controller had to co-ordinate every visual with the Tower.The answer could be varied as radar see it past my VFR traffic,route to a 5 mile final ,or no restriction.The phraseology that developed was cleared visual approach not below 3000ft.When the IFR was clear of the VFR then we said no descent restriction.
I tended to say to an IFR wanting a visual,just standby.Co-ordinate with Tower and then cleared visual approach,no descent restriction or whatever Tower wanted.The descent restriction isn't standard R/T,but if you missed it out the pilot would ask.It also cleared up confusion.