Here's my somewhat realistic, depending on moves made by us and other teams list of outfielders I could see happening. It's listed by projected WAR, although Frazier's is schewed as they don't have him getting any at bats in that outfield.
Marcell Ozuna 3.7 (This would depend on them going after a big name and needing to clear payroll and a job)
Starling Marte 3.4 (Hard to see this happening because of his value to them while Polanco is out)
AJ Pollock 3.1 (Possible, pending years)
Mitch Haniger 3 (Possible, pending prospect capital)
Travis Shaw 2.8 (would depend on who they acquire, but I think they had him on the block at the deadline, also think he could play LF for a season and mvoe to 3B when Donaldson leaves)
Joc Pederson 2.7 (very reasonable acquisition)
Max Kepler 2.7 (GM has been making value moves, so he may be holding on to Max seeing the breakout possibility)
Whit Merrifield 2.7 (Dayton should trade him. He's an idiot if he holds on to him)
David Peralta 2.6 (Should also be traded and a likely acquisition)
Chris Taylor 2.4 (If available, would be a good addition)
Corey Dickerson 2 (not much of an upgrade, but he'd be in his contract year where he could miraculously have a career year)
Ian Happ 1.5 (I'd really like Happ, but with the Russell situaiton they may keep him for his versatility. Would be a great buy low situation though)
Clint Frazier 0.2 (I'd like Frazier, but more as a replacement for Duvall teamed up with a guy like Joc and not the answer to LF)
I would say the most realistic winter acquisitions here are:
Pollock -- Braves were not willing to go 16 AAV on Brantley or Cutcheon. Pollock expected to exceed both in years in AAV. Draft pick attached as well and injury prone. This doesn't feel likely.
Merrifield -- Not an ideal fit as a LF, but versatile as hell and his OBP would seem to be a fit somewhere. Royals should be happy with what the Braves could offer, but the question is whether they are realistic about his trade value. If they value him like a breakout 5 WAR guy with lots of control, this deal does not make sense for Atlanta. If they are more realistic, it could be workable.
Peralta - Diamondbacks should be happy with what Braves have and don't have much incentive to keep him. But Braves did not like the price when they checked in. Watch him though.
Puig - you didn't mention him, but I don't think the Braves match up particularly well with the Dodgers as far as the return for the other guys. Seems like they would want something that upgraded the MLB team and it's difficult to see the Braves parting with the assets that would do that for them. But maybe the Dodgers would be happy to shed Puig's salary and take on a longer term asset in something of a dump.
Frazier - Yankees don't really have a spot for him, though I suppose they could hold him and move Gardiner. For either, they might be willing to take controllable pitching that could help their pen.
In-Season Deadline:
Corey Dickerson seems pretty obviously destined to move. The Pirates are not going to be in it. I could see them make this move in the winter, but don't see any obvious options for replacing him. I think the Pirates don't want to concede after making those odd moves at last year's deadline.
Sterling Marte - but when they do, might as well move Marte and/or Polonco if the market is right.
Ozuna - I consider him a long shot to be available, but if Cards fall out of it, they might see some reorganizing trades as something to do. Goldy, Carpenter, and maybe Ozuna might fit into that. But Ozuna's deal is pretty good and the Cards probably aren't going to be looking at full tear down.
