Last year I did this all at once, but I'll try something different this year, keeping the positions together and going a tad bit more in depth.
My Take: Ramos, Lobaton and pray for health.
2015 Reality : Even with the benefit of hindsight it's hard to see this as a bad plan. Ramos had, for the most part, been a good offensive player prior to 2015 when healthy enough to play. Sure he dipped in 2014, but only to below average and you never could rule out injury being the cause. Plus he was only 26 and the thought was that it was simply him wearing down. He hadn't played that many games at C since 2011. Finally get him healthy and everything will be fine.
But it wasn't. Everything kept moving in the wrong direction even though he was healthy. That might have been ok but the second assumption, that Lobaton would bounce back a little, didn't happen either. He had been below average but passable for 2012-13, and honestly bad in 2014. But some of that had to do with being forced to hit lefties when Ramos went down. If Ramos stays healthy the domino effect would mean Lobaton could rarely come up against a LHP and thus would produce at a usable level again. Well that did happen, Ramos was healthy, Lobaton didn't face LHP (22 PA in 2015) but he still got worse.
Does Rizzo get blame here? Not really. If this was going to fall apart you assumed it would be because Ramos would get injured and Lobaton couldn't handle an every day job. That was the iffy part that Rizzo was gambling on. Unlike every other position, he actually won this bet. Ramos stayed healthy. But it didn't matter. Ramos hit significantly worse, and that Lobaton, given the chance to face only RHP, also hit worse. A surprise crash and a disappointment? Hard to plan around that.
Out of Box : Since a trade for Lucroy would likely be too rich for the Nats blood, what about a challenge deal for Hank Conger or Tony Sanchez?
2015 Reality :Neither of these guys would have been much of an upgrade over Ramos. Conger did show some impressive pop, but almost entirely at home in Houston. So he might have been more of a threat at the plate, but not that much more. Defensively he seems to be a hell of a pitch framer but meh otherwise. Tony Sanchez is more of a question mark as he never really made it out of AAA, thanks to Cervelli. But in AAA he did nothing to force the issue, and I have to think that would be unlikely to change at the major league level.
So Conger would have made the Nats better but it's not a slam dunk. Sanchez probably wouldn't have.