I think you've touched on the core of the problem: It's Richie PLUS Jon that equals the core of Bon Jovi. Others can supply his guitar parts, but not the chemistry Richie had with Jon -- both onstage and off. That's forcing Jon to work harder to compensate, which is putting a strain on his psyche as well as his voice.
P.S. I also think their ex-record label "just said" what you did, except with "big bucks" instead of "sparkle"...
