Mustangs and high end cars have glass roofs, I like the idea only if they're Smart Glass (electrochromic) like an auto dim mirror, and they have those already. On a hardtop the sheetmetal in the center isn't doing a whole lot for structural integrity, if the chassis is stiff enough you could glass in it's place. Plus it looks like the glass roof cars have sort a roll cage. I remember they wanted to do glass roof on the 99-04 Mustangs, but the floppy 70's chassis wouldn't allow it.
I just wish Lincoln wold name their cars. "MKZ" and "MKC" that's going to get confusing at the parts counter.