I was in the building about ten years ago, when I had to see someone who was based there.
It was in a pretty bad way then, with warning signs up on some of the doors warning of unsafe floors, etc. There was a wee glass office/kiosk on the ground floor and one of the guys there told me that was where they used to issue the tickets for the folk who were emigrating on the ships leaving from Glasgow to America and Australia. He could have been spinning me a tale, but it was an interesting old building and I knew it had been a shipping office of some sort.
I always thought it would have been a good idea, given its (supposed) history, to have based a family/local history centre there, pulling together the various sources of info, such as parish records, BMD and valuation records for the tourists who wanted to trace their ancestors.
It would have been great alongside the old sheds (now, sadly gone), where we could have copied some U.S. cities and made them into cafes, shops and markets, linked to the city centre by a tram line.