Champions Tour won't cannibalize the main Tour by any stretch of the imagination. Not more than the the void of the Big 5 leaving would anyway.
What I think will happen is those dudes will get all the coaching roles in Laver Cup type events and stuff. Maybe they even mixed in senior matches in Laver Cup, or 'mixed' doubles with Legends and active ATP players.
I can tell you for the Canadian Open I've seen senior matches between the likes of Agassi & Courier get more butts in the seats than R16 matches. And no flack to Courier but....yeah.
I think pairing with Masters or even 500 tournaments would be a smart business bet, but Murray might not be able to play even at that level if his pain is that severe. Becker doesn't really go out there with his knees.
But health permitting, yeah, especially Indian Wells. Could be a nice Semifinal pairing.
If Federer played on the Senior Tour, his first round matches would get higher draws than Slam finals. I don't know about you but I'd rather watch a Fed/Roddick match on the Senior Tour than an Anderson/Cilic Wimbledon final.
I like the idea but there'd be many problems in trying to make this any kind of long term thing, chief among them being that none of the big 5, for various reasons, seem much interested in competition if they aren't vying to be the absolute best in the world.
Because of this, and other issues, I think you can only hope for what I think we'll ultimately get: the occasional tournament featuring one or a couple of them, and numerous exhibition matches for their academies and other charities. Bet the Big 4 will play a doubles match at some point.
That said, I already cannot wait to watch the first senior event to nab all of them, plus a Tsonga/Roddick/Hewitt/Delpo-type undercard.