That's the rub - the Brewers are gaining more from parking lots than development. The city would gain more from development than parking lots. I think the Brewers would probably like to develop some of that land but they want the same tax deal they have now.
The vacancy rate for apartments in Milwaukee is 6.6%. Plenty of people would live there. Some mid rise apartments, townhomes along the river, add a hotel, a brewery, office space, etc. What was once a sea of parking is now a lot of buildings. And there's a bunch of retail a mile south of there - it's not as isolated as it looks.