I think that you've raised one of the trickiest and most interesting aspects of this whole situation. I alluded to it briefly in one of my earlier posts. In 2015, scenario 1 actually gives you more roster flexibility since Heyward's salary is lower than Markakis and Miller (I haven't seen the details of Markakis' contract but I'm assuming it is 11M each year). But in 2016-2018, scenario 1 gives you less roster flexibility. There are various ways to try to mitigate or deal with that. If there was a way to move part of the Melvin or CJ contracts by 2016, that would be one way to mitigate it. But there is also the possibility (if there is no market at all for Melvin or CJ) that we would have to resort to a less appealing option by 2016 0r 2017 (such as moving or non-tendering some of the guys that will getting more expensive by then (Gattis, Minor, Miller, Teheran, Simmons, Kimbrel). You could also mitigate it by structuring the Heyward contract a certain way. Backloading. Or even the reverse, increasing his 2015 salary for some relief in 2016 or 2017, or some combination of that and backloading.
There are lots of possibilities. One that has particular appeal to me would be to flip Gattis as he gets more expensive to an American League team for a pre-arb outfielder.