If Stepan goes to Arizona, the Rangers are going to get futures in return. Arizona needs to reach the cap floor. With Smith traded, they'll have $15 million to go even if they bring Doan back one more year.
The Rangers will get 2-3 of the 7th overall, 23rd overall, Dvorak, Domi, or Fischer. That's minimal salary coming back to the Rangers. The value in doing such a deal for the Rangers is to re-stock the prospect cupboard and to free up cap space to sign a guy like Shattenkirk.
If Stepan is traded and Lindberg is lost to expansion, the Rangers have no choice but to dip into free agency to find a checking center or two.
I wouldn't hesitate to bring Brian Boyle back at all if he'll accept a deal for under two million/year for a couple of years.
Bonino would be a great target but will be overpaid because he won two Cups in a row with Pittsburgh. Martin Hanzal would be a great under the radar signing. He went up against the Western Conference's top centers for years with Phoenix and did a great job. He'd be an ideal top 9 checking line center that would be able to slide up and down the lineup in case of injury. He'd be a bargain if he'd sign for under $4 million.