" Prey that can persist without extirpation, that remain small and vulnerable to predators throughout life, have high reproduction rates, produce large crops of offspring relative to their standing weight, exploit lower trophic levels, and have short spans of life that turnover the population are what I would consider "ideal" for this purpose."

I like this. This is also one of the reasons I felt the Red shiner would fit well. They seldom achieve a size larger than 3" but have the same body mass as a slightly larger GSH without the potential of outgrowing the predator and turning the table as GSH do.
I have many thoughts on this but am enjoying the reading too much at this point. :-))