I personally don't like the cherry on top of a cake or ice cream sundae... I'm more whip cream type of a guy and its all about the cream in the middle...
But back to the topic at hand... I wouldn't consider Merriman the cherry... He's definitely not the cream filling... Kyle, Dareus and Mario are the core components of this D... Merriman would have to be the writing on top of the cake... If you have a nice decorated cake, it looks fine and all but, what's the celebration? Happy new year? Happy birthday? Merriman would be the writing on top IMO and give a clear understanding of what we are celebrating which would say, "Welcome Back Bills Pass Rush"...