It's not a "Wilmington" FM. The transmitter is all the way down towards Bridgeton, NJ and it's only a Class A.
The Philly stations have much better signals than 101.7 in Wilmington itself. It's actually pretty amazing that 101.7 manages to get a 2 share. I'm not sure what else you could do with that signal.
A Rock station for Wilmington would seem like a natural fit, since all of Wilmington's FM's are female-leaning. However, when 94.7 RDX tried Rock a number of years back, they failed, and 94.7 is a better signal in most of New Castle and Cecil counties compared to 101.7.
A hard Alternative station would be too small of a niche for Wilmington, class B or no class B (and because of Southern DE's 101.7, WJKS can't upgrade). If you look at what is currently working and has worked in the past in the market, it's broad-based AC and CHR formats.