Offensively, they are likely similar (though Pennington plays in a giant park). So let's just say that he does become the .700 OPS guy Pennington was before this season. Well, that makes him a slightly below average offensive shortstop. Toss in plus defense and we now have a slightly above-average overall shortstop. Sure, he won't be Tulo. Still a lot of value there.
We already are doing better. The +/- system that Dewan/BIS are doing is better. The field F/X system, while not really being shared with the public, assuming it is working like they say, it already vastly better too. In fact, it is probably the best thing you are ever going to be able to get if it works right.
Well, they are better for 2013 as long as Choo or Bruce can play center adequately and Cozart plays 150 games. If one of those two things can't happen, things are murky as if the Reds are actually better.
For an actual amount of time? Who knows. There is literally no one in full season minor league baseball who is a true shortstop at this point and the backups on the Major League squad are, well, not true shortstops either.
With his defense and ability on the bases, if LaMarre can OPS .700-.750 he should probably be starting in center for someone.