I'm not trading Leary just to trade him, but I'm definitely seeing what he can bring me.
There is no way you can make the argument that a starting-caliber backup interior lineman is more valuable than a starting-caliber starting running back.
If you can get a back who is a significant upgrade (or a starting DT, or a starting safety, etc) for Leary you do it.
What you want to avoid is a trade that you should realize you are losing, like when we traded Kevin Mathis (who went on to play many productive seasons in Atlanta) for Chris Bordano (who was a waste of space).
But if you can get a young-ish RB like Lamar Miller, go for it.
The decision is made that much easier because Bernadeau is here. So you can't claim that you are scraping the bottom of the barrel if an injury occurs, because Bernadeau is a solid backup who at least won't embarrass you if he has to play.