Is converting a wrestler to OL a dumb idea? How about converting a small QB to slot receiveer or an OLB to a TE red zone threat? It's called thinking outside the box, which BB does more than any other head coach in the NFL.
I hear what you're saying, but unless Cannon played some DL in college, I don't see it happening. The skill sets are completely different for OL and DL.
For one thing, Cannon would have to learn how to tackle. Not so easy to do when the guys you're practicing against are NFL players.
For another, Cannon would need to forget everything he's learned about playing o-line and start from scratch, learning all sorts of new d-line techniques. As we've seen with a guy like Ron Brace, it takes more than size, strength, or athleticism to become a good DL.
Third, I believe we have a far greater need for Cannon's talents on the OL. He was an offensive guard in college, and we need potential starters at guard this year in the event that Mankins holds out or Koppen/Connolly gets hurt. Not to mention that making Cannon a starter at RG and moving Connolly to C could be a huge upgrade to our line from a physical standpoint (and is a plausible scenario if Koppen misses a few games). Unless you want to count on Ryan Wendell as a potential everyday starter, we need Cannon on the OL.
On the DL, we already have a ton of young talent. They all need a chance to develop and prove whether or not they can play in the NFL. Brace, Deaderick, Pryor, and Kyle Love are all guys who can offer the same strength and size that Cannon could as a DL. But none of them are starting from the ground up when it comes to technique, as Cannon would be.
From a pure size/strength standpoint, moving Cannon to DL might make some sense. But when you actually look at the roster, I think it becomes clear pretty quickly that we need talented youth at the interior o-line positions. And I think it's much harder to move from OL to DL than you might imagine.