I'm young and I have a lot of fire... but I doubt I'd be a good coach.
That's being extreme, I know... but my point is that the person needs to be a good football coach first and foremost. You can't just go grab any young, currently hot coordinator and be assured of success any more than you can be with a re-tread like Dungy, Holmgren, Shanny, etc.
I don't really disagree with you because I too would like a younger, tougher guy as the Dallas HC. But there's a lot of risk when giving a guy his first head coaching job... more risk than hiring a historically successful re-tread.
However, the possible reward is greater too.
If I were Jerry, I'd probably try to get a guy like Shanny, Cowher, or Holmgren and let them groom a young, firey coach to continue what they start in Dallas... and as the owner I would insist that what they start would be a tough, hardnosed, disciplined style of football that pays a lot of attention to the fundementals.