I agree that those are the guys the ones that won't be there at training camp.
I think it comes down to how Parnell does the next two games. If it looks like he can start competently (and by that I mean a little below average for a starter but not atrocious like Free has been sometimes), then I say Safety. But if it looks like he can't hold up, you have no CHOICE but to go RT...there's no one on the team that can play the position.
I say safety over the other positions because I think safety is the one upgrade that will enhance the ability for us to utilize other players to their strengths.
I think Livings has been good, Costa's ability as an in-line run blocker I think will help alleviate some of Bernadeau's deficiencies (also, bernadeua is still young and can improve himself, and there's a decent chance that Arkin or Leary could step up next year). But I think when you look at the offense, you have a quarterback and a running back that are able to overcome deficiencies in the oline because of their skill set, and that's why it's less of a priority to make major upgrades there.
I think we have a great NT in ratliff (he's been great this when he hasn't been injured, no reason to think these injuries will continue next year, he's never had an injury problem before), and we can sub in lissemore to back him up.
In terms of 3-4 DE, Hatcher has been playing at a very high level, I think Crawford has potential, and then Spears is competent to sub in.
But adding a true free safety would be huge. We're playing sensebaugh out of position (he's best in man coverage on tight ends or in the box, not in deep zones), we're playing carr outside his skillset (press coverage) because we don't have faith in our safety play.
I don't think adding a 3-4 DE, NT, RT, OG, OC, will help IMPROVE the individual play of other players by allowing them to focus on what they're best at.