At this point there probably isn’t any real difference between Tucker and Markakis and obviously they don’t complement each other in terms of skill set or platooning. In a vacuum, the move would be to trade Markakis and play Tucker/Bourjos/Adams in a rotation. The problem, however, is no one is going to take Markakis’s contract off our hands and as long as we are semi-contending he’s going to have value for the 2018 squad. The real cost of calling up Acuna now is it removes Tucker from an everyday role where there’s a non-zero chance he could become a cheap, somewhat permanent fixture in LF. In my opinion, that’s a much more important dilemma than getting Acuna an extra 50-100 MLB at bats. The focus should always be towards 2019.
Ideally, Tucker and Markakis both continue to play well, Markakis is traded to a contending team who is willing to cover at least half of his remaining salary, and Acuna is called up to take over in RF. Hopefully that can all happen before June rolls around.
The only problem in this scenario is that if Tucker and Markakis are both playing well then the Braves could very well be a WC contender. And as you said if the Braves are intend in that spot I doubt Neck is traded.