First, good OP, Sir...and it was a good one going immediately into Training Camp.
My first thought, was of Flozell Adams, 'Hotel,' and him playing guard his first season to get a feel of the climate before moving out. That could be wisdom here.
My second thought was an appreciation on the knee braces being worn and how that might affect the longevity of Ronald Leary. This is not a small matter in my eyes.
A background thought could be the pass blocking ability of Uche Nwaneri, and this could solidify any thoughts to moving Zach Martin outside.
I very much like the inside combinations that involved with the presence of Travis Frederick, Leary, Nwaneri, and Mackenzy Bernadeau.
I think that the future at left tackle is as important a decision as the OP points towards. Like X stated, I do like the development of Jermey Parnell. I'd like to see a definitive decision made upon him now. He does remind me of a player developing, such as Mark Tuinei. But another concern, is the need to keep options open this next season for the defensive box area. Parnell would be sweet if he does leave solid footprints further as to his career outside. He would meet a needed value if he does...or Doug Free gets another contract.