I loved Lewis, but now he has a major knee injury on his resume. I wouldn't trade Inciarte for him anymore. Inciarte is the one and only truly valuable piece the Braves can afford to trade away, so if he's traded the return needs to immediately improve a position of need (3B or C).
I understand what you are saying and you are probably on the line of the FO thinking BUT I think it's wrong. Having a guy you can stand at 3B or C in 2017 is much less important than having that player there for 2018 and 2019 (and in reality 2022) IMO.
Trading Inciarte for a guy like Baez who could come in and start day one at 3B would help immediately in 2017 and assuming continued level of play or even progression, would help through 2021. But, it fills just one position while vacating another position (where you hope M Smith is the equivalent backfill). And, you're looking at a guy who becomes a significant part of your payroll obligations at about the time when you can reasonably expect the rebuild to bear fruit. So he might make $1M in 2017, $5M in 2018, $10M in 2019, $15M in 2020 and $20M in 2021 then be a FA.
OTOH, if you turn Inciarte into two starters, as an example Happ and Jimenez (let's leave the discussion if that would even be possible, assume something close to that return) then Inciarte brings little to no help for 2017, but that's OK because 2017 isn't a realistic year anyway. But say Happ and Jimenez take over the corner OF spots sometime in 2018, then 1. That allows you to move the cost of Kemp and Markakis (if you can) so immediate cost savings 2. Allows you to have two starting OF who would cost you less than Baez would cost you over the time period of 2018 - 2021
combined - H&J combined $1M in 2018, $2M in 2019, $10M in 2020, $20M in 2021
roughly, plus you have BOTH for at least 2 additional years beyond where you would potentially lose Baez.
So, lets assume the second deal, Inciarte for Happ and Jimenez, that still leaves 3B and C as potential weak spots. BUT, you've saved yourself some money which
could be used to improve those spots through FA by signing guys like a Lucroy or a Machado or Arrenado.