Plus they tend to attack other fish more.

bowfin eat sunnies for breakfast. not to mention lunch and dinner. in fact, all the bigger fish (pike, walleye, muskie, etc) will tear up sunfish. they're the "middle" part of the food chain. they eat the smaller fish, and they get eaten by the big ones.
besides, if you're going to put bass in the tank, you've already got sunnies.
I'm not trying to push them one you, but you did say an ecosystem type tank and sunfish are nearly omnipresent in the U.S., it's hard for me to imagine that type of setup without them.