There hasn't been a lot of success with upstart CHR competitors to heritage outlets in recent years. KAMP/LA has probably done the best, but they still haven't been able to beat KIIS even with a high profile morning show and lots of promotion. The AMP station in Detroit hasn't come close to topping longtime hit station WKQI, and 92.3 Now in New York has been no threat to Z-100 at all. Why would it work here, especially when Kiss 108 has Jam'n flanking them on the rhythmic end? CC will do whatever it takes to swat down any challenge, like they've done in LA, Detroit and New York.
The format hole that's the most glaring in Boston? Believe it or not, is Spanish/Tropical. An all Spanish FM would make a serious dent 6+. Don't know how saleable it would be, but I bet it would do better than a full blown Urban or Urban AC.