Another question is, how many players from 2005 would start for the 2012 team?
Leroy Hill is an obvious exception since he started for both, but I wouldn't pick a single player from 2005 defense over their 2012 counterparts
On offense, obviously Walt and Hutch are gimmes (though Okung is having a stellar year and deserves an honourable mention), after that it's pretty much personal preference - I don't think there'd be a significant dropoff either way if you switched Tate and Rice for Jurevicius and D-Jack, Engram would obviously be first choice over Baldwin, but even then the dropoff isn't significant, I'll leave the Alexander/Lynch, Hasselbeck/Wilson choices out of it as we've had enough discussion over them, Strong is the superior fullback but once again the dropoff to Robinson isn't huge, Unger is probably a better center than Tobeck was, and I'd take December Giacomini over 2005 Locklear (who I'd take over September Giacomini), Miller and McCoy are no doubt preferably to Stevens at TE.
All in all, the 2005 offense probably has a slight advantage, but not a significant one, and one that is totally negated by the quality of our defense and special teams.
The bend-don't-break quality of the 2005 defense would be useless against Russell "always scores in the red-zone" Wilson (longest active streak in NFL)
Tatupu would start without question. I'd probably take 2005 Trufant over 2012 Browner. Think the 2005 WR corps was better once you go four deep. Otherwise I agree with your assessments.