If we are serious about finding a CF or an SS, then I don't mind having ONE of Revere or Espinosa back as a 4th OF / backup infielder. That's one - just one. Lobaton is the only other final year arbitration guy, but I think you make an offer for him and either go with him and Severino and perhaps try to sign Ramos to rehab; look for him to be your late season addition rather than needing to trade. Right now, the veteran bench depth of Heisey and Drew are gone, so that needs to be replaced.
Just to know what is coming, besides the last year arb guys and Werth, the other contract expiring after 2017 is Perez. Petit I think has an option that can be exercised for 2017. In addition to Murphy and Harper, Kelley is off the books after 2018.
MDS is onto to something. It may be time to figure out what this team will look like after 2017 / 2018 time frame. There's Turner, and what else? Even Murphy's contract expires after 2018. Do you try a blockbuster built around Rendon or Harper? Rendon has team control through 2019, so I think he's a piece to build around. Roark also has team control through 2019.
A guy on the Dodgers I'd be tempted to chase might be Josh Reddick to play a corner post-Werth. Use Harper to plug maybe two positions, sign Reddick, hope Robles is your solution in one of the outfield spots by May 2018. For grins and giggles, something like Harper plus Ross for Swihart, Benintendi, and Ed Rod gives you the catcher, CF, and lefty rotation piece while they backfill for Ortiz with a huge bat and even some speed and get a righty into their rotation. They have the resources to sign Bryce long term, too, and get at least a 2 year run with him. I'm valuing team control and cost for the Nats as well as the talent in the targets.