I did my initial training at a controlled airport. There were about 4 international flights a day and 20 or so RPT. Helicopter training and instrument approach training plus the Aero Club with its 2 x 152, 3 x 172s, 2 x PA28-181s & a twin Comanche. There were 3 full time instructors (CFI + 2) & about 12 part time. Everything was easy as with ATC using binoculars, radio and the old ticket system.
Then in the 90s a British Flight Training company called CTC arrived & built a dormitory, offices & hangars & eventually had 40 odd Diamond DA20s & 40s operating. The controllers were very busy at times but it all worked well but it did mean a lot more orbits at different times for sometimes several aircraft when a Saab, ATR, 737 or A32O was on the way.
Everything worked and I can't remember any situations occurring.
This is over the top for somewhere like Cowra but maybe there is a case for CA/GRS that has been in place at Ballina for a few years now. A tower is planned for Ballina so then the CA/GRS will disappear. It would mean improved safety and situational awareness but would add landing fees.