Mark -
At least in Atlanta, Turner Field is pretty strictly a baseball park. OTOH, it predecessor, the NLE Fulton County Stadium, was built to be a multi-purpose facility. Seating could be changed for the Falcons and college football games. In another variant it could be used for concerts. I saw the Beatles there in the 60's, for example.
The Ted's current narrower mission is possible in large part because enclosed facilities for non-baseball events were built in the last 15 years. There is now less need for a multi-purpose ballpark.
I am not as familiar with those sorts of issues in other cities.
But whether or not other functions are feasible at these new parks, the main motivation behind them (to reprise the theme of my earlier post) was - not unlike the return to Golden Age design ideas in golf courses built in 90's and later - to have ballparks that captured the feel of older ballparks like Fenway and Wrigley. Seating is closer to the field to increase intimacy. Seating capacity is reduced to enhance the coziness. Sightlines are improved and so forth. In short, the main goal is to make attending baseball games more fun.
All ideas, if I might be permitted, taken from "Golden Age" ballparks built before WWI.
Bob