Sure. Why not? After all, if Tomlin has one true skill, it's the ability to control a diva and turn them into a team player. I'm sure he'd fall right into line and do anything to help win that championship.
Sorry. I'm not a Tomlin hater but I will freely admit a marked weakness on his part is that he lets the 'players' run the asylum. It's the downside of being a 'player's coach.' (One symptom: He freely admits he hates the extended celebrations yet does nothing to stop them.) The Steelers have always had a good core of dedicated players to limitedly reign in that kind of behavior but most of those guys are gone. Ben talks the talk but I don't think he actually inspires the young players to knuckle down.
Anyway, I guess my drunken rambling point is that I really can't think of any current player who would probably do more locker room damage to the Steelers right now than Dez. If they signed him you better hope he has 50 touchdowns by week 6, otherwise he'll be playing for the patsies for the league minimum by week 8.
I can think of no worse FA.