Warfarin

Truth be told, I find more satisfaction from the "under the radar" moves that pan out, like Bridwell.

This highlights the huge benefit of acquiring Cesar Hernandez.  We'd go from a -1.2 WAR at 2B to a 3.3 WAR, or a 5+ WAR turnaround.  I know past performance does not guarantee future returns, but assuming no drastic changes, that's a significant turnaround at a single position, and it's a reason as to why I think second base is the prime target this offseason.
If we can improve either 1B or 3B (whichever ends up being the better value play), then we could possibly add another 2-3 WAR in that spot, or a 7-8 WAR turnaround in offseason at just two positions.  Combine that with a full season of Upton, some (hopefully) improved health from SP, a (hopefully) full season from Trout, and that's a huge improvement from one season to the next.

Those are some excellent points.
I do feel it's unlikely we'll see BOTH corner IF spots upgraded in a single offseason.  We have Valbuena, Cron, and Marte who can all, to some extent, play some kind of role.  I would also prefer not to have several corner IFers locked down to a multi-year contract, knowing that we'll need some dollars to upgrade other positions soon (i.e. catcher, as Maldonado is entering the last year of his contract) in the upcoming offseasons.
I like Santana's offensive game better than Moose's.  He has a better eye and grasp of the strike zone, as evidence by his nearly 1:1 BB/K ratio.  My concern with Santana is he is at the age where decline usually happens, and I feel we'd be paying him for his past accomplishments and not for future contributions.  I'd strongly consider LoMo too.  It concerns me that he's only had the one good year in his contract season, but if we can sign him to a 2/24-ish type contract, then that helps mitigate risk, since even if he proves to be a fluke, we'd just be stuck with him for 2 years.  And he also has the benefit of not costing any draft compensation.
With Moose, if he indeed gets an offer for 5 years, then let him go elsewhere, no biggie.  There aren' many contenders looking for a 3B, and if you recall last offseason, Justin Turner signed at a considerably under-market contract to stay with the Dodgers (most thought he'd get 5 years, too).  I think some of the big market teams that want a stud 3B will wait next offseason for Machado to hit the market.  So with Moose, I say only sign him *IF* you can get him at a below-market value.  I know people say that's unlikely with Boras, so again, if this is true, then forget it.
All that said, if we can acquire Hernandez (my #1 offseason target) and Santana, then I'd say that's a pretty successful offseason.  I'd like to acquire a lefty reliever as well (Minor?  McGee?  someone else?), but I feel we can possibly fill that cheaply as well if those options prove to be too expensive.
Lineup:
2B  Hernandez (S)
CF Trout (R)
1B Santana (S)
LF Upton (R)
DH Pujols (R) **I'd bump him lower but realize that's unlikely**
RF Calhoun (L)
3B Valbuena / Marte platoon
SS Simmons (R)
C Maldonado (R)
This works out well, too.