Santana can play 1B and 3B and he's a switch hitter, expensive bench piece but we can afford to keep him if no one makes a decent offer, it's just Middleton's money. Only two years left on his deal, and if Franco becomes a dependable bat, he can be moved in July.
Ramos is worth it on a 2 year deal if he has the personality to be a mentor, you have to pay him on the basis he'll play 80 games or so. So it takes care of himself, if he wants more money (and someone offers it) he goes.
We're not getting Machado, in what universe would he want to come here? Money isn't going to make his decision.
Harper at the right price is a possibility, but he's far too inconsistent to give a megadeal, he's a 5 year, $150-175M type deal, not a $10 year, $350M overpay that can cripple your franchise (doubtful the Dodgers will take him off our hands!). In five years he'll probably be a seriously negative fielding corner OF, so he'd have to maintain a plus plus value to have value, so you don't want to commit that long.
We're not going to be competitive in 2019 unless the core improves, this fantasy of buying a WS is just that, if your base isn't good for 85-90 wins, free agents aren't going to be difference makers. Arrieta is the most likely outcome, an overpay that adds limited value. We need to play the kids next year and find out who belongs in the long-run. If we add free agents, anyone over 30 should be on Santana/Arrieta 3 year deals that won't block resigning the core. This season showed that adding a bunch of solid veterans isn't enough if the kids aren't ready.
The real key is improvement by young players, Eflin with his changeup, Pivetta, the young bullpen, Crawford, Kingery, Franco, Quinn, Williams, Hoskins, Alfaro, and developing some players like Haseley for the second half. Can we put the fantasy baseball "buy a winning team" scenarios to rest? We're not the Yankees or Dodgers,and both of them have focused on player development (Darvish was allowed to walk, Yankees are becoming mostly homegrown) because they cvouldn't make the buy a flag strategy work anymore (see the Red Sox for another convert).