The more I think about it I think Thornton is a bad idea. We would be competing with other teams to trade talented youth of the future for a player that may start to decline at any moment - too much of a gamble (we are essentially trading for a player that will never be better than he is now).
I would rather trade more for a player that could have a long term future with the franchise. Could be a youngish Dman, could be someone like O'Reilly, could be anyone with a long term future. I think Kesler (age 30) is as old as I would entertain trading assets for at this point.
P.S. does O'Reilly have to stay with the Aves for another season after arbitration before being traded again? I remember last time he went through arbitration he couldn't be traded for a while.