Bay City really isn't opposed to the idea at all. Disc golf is an occasional hobby of the Parks and Rec Director actually (how occasional, I don't know). The problem really is physical space/land, and then who owns that land. Examine the city in Google Maps, find a spot, find out who actually owns the land, and propose it. The city is more than willing to listen. The county executive would be optimistic. Any commissioner would be willing to support it also, I bet. Growth is good.
My personal opinion is that a good location for a disc golf course in Bay City might not exist, and we're very fortunate to have Memorial Park, Wickes Woods, Tittabawassee Trails, Chippewa Banks, and The Jungle within a 30-40min drive. Not to mention Deerfield Park, Holly Woods, Goldenrod, and Grayling Rotary are within 60-75min of Bay City.
That being said, the only other possible location I can think of that wasn't fully explored was the old Alkali property. At the request of the city, I personally collected over 15 letters of recommendation from communities around Michigan with disc golf courses and submitted them as part of the original middle grounds proposal. They could still be used. I'd be happy to pass them on...