There are a number of possibilities for reuse. The most interesting remains the use it was intended for chiefly a railway station for interurban travel, but also a revamp of public transit involving steetrail or trams and bus hub. This project by a public transit planner in Detroit was initiated to further that purpose. It is very well thought out and I think the future of transit in Detroit resides in a restoration of potent structures such as MCS in order that detroiters reconnect with their past. Detroit has a fabled past in transit, tourism and retail which is largely evacuated. There is a need for historical reeducation as well as novelty in infrastructure so that retail, residential reinvestment and tourism can be revived.
http://fwrail.org/