Using the Central Station as a hub a subway system can be create that branches out to all of metro Detroit. An undertaking like that can be painfully expensive but if stations were located by, on top of, or under businesses passengers wold be directly exposed to the goods offered by those businesses. To have this privilege the business would contribute to the initial investment of building the required infrastructure. As a result the participating businesses would see a huge increase in customers. This would be a way for the metro area as a whole to take part in the building project.
Additionally it would make it much easier for the residents of metro Detroit to get into the city and experience all it has to offer.