To answer a few points...
Commons is 100% left footed, but he isn't afraid of using his right foot; very decent cross of the ball with both feet. He is playing just off the strikers for Derby County at the moment, but has been used on both wings by club and country.
Naysmith is a weak link, but has experience on his side for this important game. I'd like to see Alexander playing left back, as he has shown twice against France that he is more than capable of shackling players that look to cut inside. McAllister has been playing very well for Bristol for more than a couple of seasons and deserves to be in the squad.
Broadfoot and Barr are in the squad for versatility and experience respectively. They are backups and will be warming the bench for both games, unless injury and suspension kick in.
Gary O'Connor isn't in the squad because he's only just come back from 5 months out injured. Came on as a sub for last 20mins in the last Birmingham game. He still needs to prove he has the right attitude, after all the messing about he did in the last campaign.
Our centre defence will be Weir and McManus, as Burley has an agreement with Weir that he'll only call him up if he plans on playing him. As a result it'll be Caldwell sitting in front of the defence instead of Hartley, as Caldwell has done for Celtic recently and he did v. France at home.
Injuries permitting the team will be
-----------------------Gordon-------------------------
Hutton--------Weir--------------McManus-----Naysmith
----------------------Caldwell--------------------------
-------Fletcher------Ferguson--------Brown--------
---------------------Commons-----------------------
---------------------Miller----------------------------