Gray was injured in 2016 and the 1st month of 2017. Hasn't been on the DL at any other point in his career. So I'm pretty confident he can be healthy in 2018 as much as you can have confidence in any pitcher.
Nobody is even suggesting to come close to Cashmans rumored asking price
Depth is always good in your starting rotation. But if the Braves plan to keep all of their current starters then no it doesn't make sense. But when there are plenty of ideas of moving Julio for payroll, Newk + prospects for an OF upgrade or Realmuto then that depth can evaporate pretty quick.
Which is fine in theory, and we keep kicking these moves around in discussions here - but in reality neither of these seem anywhere close to happening.
What we KNOW (as much as has been reported anyway) is that AA has been told "no" on both Haniger and Peralta thus far - until he ups what he's willing to pay (likely into the overpay range) those don't seem to be the likely OF upgrades. Doesn't mean one might not eventually happen through trade, but they don't seem to be happening right now. We also KNOW (again, more or less just surmising from the reporting) that they're not against moving Julio's salary at all, and that they see Gray as a likely upgrade - whether that's over Julio or the kids.
We also can guess that they haven't yet drummed up any interest in Julio - if they had, he'd likely be gone already. If Gray's only a slight upgrade over the Newcomb, Gausman, Soroka, Touki, Gohara, Fried crowd, Julio certainly isn't one. He's still here (and in the rotation) for two reasons - 1.) his contract, and 2.) his stuff likely doesn't play in the pen (especially since a lot of his recent troubles have come in his first inning of work). Every other team knows this as well, and I think AA's going to have a really hard time moving him without eating money or attaching a prospect at this point unless he's taking a bad contract back. If he has to do that, it kinda defeats the purpose of moving him. The only difference between Gray and Julio at this point is that Cashman has openly said they're going to move Gray, and AA hasn't said as much publicly about Julio. AA's "smarter" than Cashman in the sense that he's not out there talking about what kind of return he wants when everybody else knows they've got him over a barrel. Of course, Cashman has unlimited money to spend AND Gray's stuff will play in their pen if he doesn't at least get something of value for him - so he's not in quite as bad a position as AA is with Julio.
At this point, I'd be wearing the phone lines out talking to DMGM, Cincy, or Minnesota and offering Julio for a Competitive Balance pick, but I'm not sure he can get that for him.
Don't get me wrong, like everyone who's in favor of adding Gray, I agree he'd be a a slight upgrade - and I'm not against bringing him in. I just wouldn't do it unless AA and Cashman would expand the deal to get Frazier included, and even then I'd probably want a clear path to being able to unload Julio without eating money (which we just don't see yet).