It's a shame that a third party would have to go out of their way to personally invest in a study to present an alternative option that would save the city millions. One would think the professionals in place could run with this by evaluating it in-house.
However, right off the bat, common sense would tell me I'm saving tons by not having to construct four separate building foundations on multiple blocks, parking garages, new parking aprons, and repetitive building features such as, entryways, windows, restrooms, etc. that come with developing multiple structures. From attending the inauguration last week, the PO's exhibition hall looks to be pretty solid and in great shape. There's also acres of paved parking behind it. There's no way finding a way to reuse/modify existing facilities would save taxpayers huge bucks along with creating a more efficient intermodal complex. This is something we may have to dig up extra time to do as you suggest.
Anyway, I wonder how many years would it take to drum up $180 million for what's currently proposed? After all, this thing has been talked about since at least the 1970s. My gut feeling tells me, we'll have a new convention center built well in advance of the full JRTC plan coming into implementation. Without looking into an alternative option, we'll probably spend a ton of money building Greyhound on Adams Street, then modify after the convention center moves, leaving the greyhound terminal isolated a few blocks away. The other option would be worse. In that scenario we'd find the $180 million pot of gold at the end of the rainbow and break ground on the sprawling ranch, only to discover that the convention center moves out before construction is complete, leaving a gaping vacant hole in the middle of the complex.