There are no ponds near me that have just cats and bgill. There is one (0.2 ac) that is "cat heavy" (larger cats) although a few bass are present. This pond seems to remain fairly balanced but the large bgill and all sizes of bass are scarse; probably cat predation. Cats do not spawn there.
I am not sure how many others here have experience with just cats and bgill.
I think his would work best if the cats did not spawn. This way you have direct control of their numbers. If your rock pile structures are farily tight and openings are smallish where cats could not get into a cavity to spawn your idea has a better chance of succeeding. A nearby pond with large cement rock "condos" promoted cat spawning here. Weeds improved survival of young cats. Overabundant cats will be a turbidity problem. Your underwater structures may inhibit proper seining of the pond. .
Your pond is small, 80 ft circle (0.12acre). As you mention the big benefit here is being able to quickly drain and start over.
Here is another idea. At first try the male only bgill, feed them for growth. Maybe add a few cats for table use. When you see that you have mistakenly added a female bgill (presence of young bgill) then it is time to add the cats OR more cats for population control. This method will give you experience sorting male and female bgill. Sorting/separating is easier than you may think. The bigger the adult bgill is and the closer to spawning season, the easier it is to separate them .
As I said earlier, my main concern with numerous cats in your small pond is potential for turbidity problems if you get too many adult breeder cats. Last week we saw in a pond where a large catfish had "dug" out a cavity the size of a bushel basket in the side of a clay lined pond. The even more impressive thing about this was the cavity was dug out into and through a 8"-10" thick layer of 1"-2" limestones that were placed as a stone ledge along the upper bank wall to a depth of 3'. Saw the fish in the cavity. A very determined fish!.
