While I'm not certain that it qualifies as a "hidden" gem, Blue Mound is no question a true gem of a course.
I played it again with my cousins over Memorial Day weekend, during a quick 48-hr family reunion. My previous round was in 2004, when some of the aforementioned renovations were taking place. In addition, our host noted that tree removal was ongoing, and it was certainly noticeable to me, even given the 5 yr time difference between visits.
Many of the usual MacRaynor templates are there, including some less commonly used ones, such as the Hogsback and #1 NGLA templates. While I wouldn't necessarily hold up any of the individual interpretations of the templates as the "best of its kind", as a collective they really go well together, and fit the landscape quite nicely there. There is some rolling nature to the holes on the eastern side of the property (#5-#9, #11, #12) many of the others are on the flatter western half of the course.
Conditioning in May was excellent.
Not to steer somone away from Lawsonia, which I love as well, but I would have a hard time strenuously suggesting somone go there over BMGCC, assuming access is no issue, which I'm pretty sure it isn't!
I think both courses are a delgiht, and and if travel and access are assumed to be equally no issue, then my own personal split would be 6 Blue Mound, 4 Lawsonia