To me, the first question is 1b. If LaRoche is willing to take the option, then you do that. If not, then you try for a two year-with-a-mutual-option third extension. If that doesn't work, you let him go.
If you let him go, you've got to find a lefty with some power. Could be 1b, could be LF, could be RF. Depending on where that comes from, you make a decision as to what you're doing with Morse/Moore. Essentially, you've got two spots to play with on the field - LF and 1b, with Morse and/or Moore sliding into the other one. If LaRoche doesn't come back, you need a lefty 20-ish HR guy to round out the lineup. That's priority one.
For my part, I'm officially declaring the whale watch over. We don't need leadoff/CF. Harper's good in CF as your most-every-day starter, keeping Shark as a 4th OF and Werth as leadoff is just fine. If somebody like Parra or Span falls into your lap for one of your extra pieces (Morse/Moore + Lannan?) then fine, but otherwise, it's not worth the effort.
EJ has to be replaced, either a. with EJ, or b. with somebody nearly as good. The FA list is really uninspiring after EJ and Greinke next year, but this has to be (along with LaRoche) the most important off-season move.
It's easy to forget now, but the only reason the Nats are where they are is that the rotation was otherworldly in April/May. The offense struggled mightily and the rotation made our paltry run production stand up - 11 games in April and May we scored three runs or less and won. If we just go 5-6 in those games, we're suddenly neck-and-neck with the Braves this year. The whole team's success is predicated on having dominant starting pitching. The rotation has hid a lot of flaws this year - not resigning EJ or bringing in Greinke or somebody of that caliber is a major mistake, in my view.
So my offseason priority list:
1. Resign LaRoche (Wow). Or find a lefty bat to replace him in LF or 1b. One crazy thought: Wonder what it would cost to get Hosmer or Gordon from the Royals? Would you do Rosenbaum, Brown and Lombo?
2. Resign EJ or sign Greinke.
3. Figure out Morse vs. Moore. Once you've resolved LaRoche, it's time to figure out what to do with these guys, who are pretty similar. One of them is your LF/1b to go with whatever lefty you found for LaRoche, the other one is good trade fodder.
4. Patch up the bench. A DeRosa replacement and a backup MI are needed. Suzuki and Ramos are a platoon, Tracy leads the goons, Shark/Brown is the 4th OF, with the other one being a possible trade piece.