If the DH becomes universal, Brantley will likely have a higher AAV than Pederson. Difference may be that Brantley will probably have a shorter contract in terms of years. Pederson is 28 and may go years over AAV, which would be a sticking point for the Braves in my estimation. I like the idea of a Pederson/Duvall platoon.
A Pederson/Duvall platoon would be great - not arguing that it wouldn't. The question is where does the money for that come from?
For the sake of this discussion using round numbers, 2021 commitments are around $82 million and an expectation for Opening day 2021 payroll is ~ $115-$120 million - leaving AA $30-$35 million to spend.
Duvall, Dansby, and Fried will get pretty significant raises which will eat up $8 million (?) or more. $27 million left.
Re-sign Melancon for $8 million. $19 million left.
Veteran SP for $8-$10 million. $9-$11 million left.
That doesn't leave very much to spend on a DH and platoon-mate for either Duvall or Riley (much less both). You'll also need to sign a utility IF (Camargo walks) and potentially another pen arm if you don't use Newk/Touki/Wilson/etc. out there. The DH definitely needs to be able to play passable defense in LF - at least until whenever Pache is added to the roster, and probably even after that.
The reason I like Brantley so much better than Pederson is that he DOESN'T need a platoon-mate. He can DH against lefties when Duvall is playing and take his place when he needs to sit. If you sign Pederson, he's strictly a part-time player no matter what - you're not going to let him DH against lefties so Duvall can play against them.
Unless AA goes cheap (which he hopefully can WITHOUT signing complete gambles), the money probably just isn't going to be there to have a strict platoon at either 3B or LF. Maybe the offers are incredibly low for free-agents this winter, but I can't imagine they're going to be low enough to provide the flexibility AA will need - contenders are still going to do what it takes to sign quality players rather than question marks. Maybe you get a hometown discount on a 1 year deal for Melancon, but he's not going to take $4 million. Maybe you get a solid SP like Leake on a 1 year deal since he already had a big payday, but he probably ain't taking $4 million either.
He COULD jump out there early to try to sign a DH/OF and platoon 3B or LF and hope to wait out Pitchers until the markets drop, but that puts him right back in the same spot he's been in all year - an unsettled rotation and a pen with even more question marks than in 2020 with no Melancon, Greene, or Jackson.