They can make a few classics an hour fly if they simply cut out the Imagine Dragons, Muse, Coldplay and whatever other wimpy sounding alt rock tracks they happen to be playing right now and replace it with Disturbed, A7X, Bullet for my Valentine, Nine Inch Nails, Three Days Grace, etc. When Bone and Rock 100.5 "became one," the playlist still sounded too much like the old Rock 100.5. At the moment, it sounds like a bad mix of the old Rock 100.5 and 99X (they need to give it up already; the 99X brand has been miserably executed for the past decade. Cumulus doesn't know how to program alt rock...period).
The other option would be to weed out most of the Classic Rock and tighten up the alt rock categories while including more hard charging Active Rock, but apparently that isn't an acceptable option, per the intel posted earlier.
I cannot even think of the last format change in a Top 25 market that Cumulus has pulled off successfully. Any successful stations they have in those markets were inherited from other companies in recent years or are heritage stations that have been around for 20+ years. Say what you want about Clear Channel (I'm not a big fan of theirs personally), but in most large markets their track record with regard to format changes & format tweaks -- especially on the FM dial -- is better than that of Cumulus.