A pretty solid effort overall I would say Jacko. I'm sure my thoughts will develop in the offseason, but my initial thoughts...
Not sure about Iannetta, but the idea seems solid. I think the Sox are about two years from having their internal catching options sort out who has which skills, so they need someone. There is little chance that they resign Tek and I think with V-Mart's bat being a bit down he won't get the aggressive offer he might have otherwise.
Overall, I think they are going to offer Beltre and Martinez basically what they could be assured they won't get a bad return on their investment and see who takes the offer. I don't think they have a master plan, they just have ways of structuring offers to not get screwed. That has resulted in most FAs leaving in recent memory, and I can see that happening again.
An even more conservative "lets not get screwed" option would have Lowrie playing 3B, or moving Scutaro there and moving Lowrie to SS. Lowrie is a competent hitter and could serve as a stop-gap/super utility switch hitter if they didn't want to get screwed.
I imagine they are hesitant to move Youkilis off of 3B unless they absolutely have to. It is probably naive of me, but I can see the Sox and Beltre finding a reasonable compromise for 3-4 years. Theo has always liked Beltre and he hasn't disappointed so far; like you, I'm skeptical of Beltre for the long haul but 3B isn't a position that has much coming up via FA. Fenway is a good fit for him and his defense is appropriately valued by this team.
They will definitely keep themselves open for either Gonzalez, Fielder or Pujols (should the stars align and Pujols is looking to go elsewhere). If they didn't go after Dunn two years ago I don't imagine them going after him now. I have no clue why that is, possibly due to his lack of defensive skills or versatility. His OBP/SLG combination makes him seem like an obvious option for DH at least.
Werth could be a good addition and he would definitely be well suited to Fenway. I'm worried that his contract could become a regret in the 3rd and 4th years, especially if the farm system is producing good OFs who are stuck at AAA because of longterm deals (a la JD Drew). I think Theo will try to stay as flexable as possible until the next Teixeira situation presents itself.
Frankly, if he were going to be aggressive on an OF contract, I see a lot more reason to make it Carl Crawford.
Couldn't have said it better.