I re-read your post, DU. You're in TX, right? If so, it's a very reasonable goal to produce both 8-10 pound bass and 8-10" bluegill in the same pond. If you were talking the extreme top end of both species, i.e. 14-plus-pound LMB and 2-pound bluegill, that would be very difficult. But for your region, those are quite doable goals. I fished a pond a couple months ago in MS from which I caught several bluegill well over 10", and that same pond has produced multiple LMB over ten pounds in the past year. And that pond isn't fed.
You just have to keep the pond well in balance, well below its total maximum carrying capacity. You can do that either through harvest of both species, or an additional predator, which is my preference because it's more constant and sustaining as long as you keep the predators stocked (pike/muskie won't spawn in TX, especially if you go with tiger muskie which are sterile). If I were in TX I could get your pond to having 8-lb. LMB and 10" bluegill in four years, possibly sooner. You should fertilize once a month from March through October, install at least two and preferably four or five automatic feeders, and keep the populations of both species balanced. If you've got an ample budget for the pond, you could have as many as two feeders per acre, which would turbo-charge the growth of the bluegill and bass both, the bluegill directly and the bass through the bluegill, by way of more good-sized meals for the bass in the form of more 5-8" bluegill and more reproduction of the bluegill.
