It's far-fetched, someone will need to find a *ton* of investment capital that companies and/or states wouldn't mind seeing practically no return on.

What about Belle Isle? There are several, mostly abandoned buildings that could be renovated into exhibition halls. There are large, empty plots of land that could be used for new development, without wrecking the picnic or wildlife areas. The old zoo could be torn down for more space. The aquarium could be renovated. Put parking and a visitor's center on the brownfield next to the bridge and have ferries move people back and forth. Heck, have a ferry depart from Hart Plaza, which is fairly central to most downtown hotels.

Then, if nobody wants to use the buildings for anything else [[they seem to get turned into museums, mostly) who cares? At least they aren't another set of derelict buildings gumming up downtown.