Could the Nats swap Wieters and Soto for Realmuto and Ziegler? That would basically have the Nats take on more money, and the Fish could get out from under Ziegler's 9 Million and whatever they would pay Realmuto for Wieters's 10.5 Million.
That would shore up the pen a bit more, fix catcher for the next few seasons, and since they are probably already over the tax threshold this year, they could still go out and sign a starter. I won't believe that the Nats aren't in on Arrieta until he signs with a different team.
I don't know why the Marlins would be interested in Wieters in a return, unless we're basically going to pay almost all of his salary. In that case, why do that if you're the Nats? Just keep him as a backup unless somehow another team is interested in him. I would love to acquire Realmuto somehow, but trades within the same division are rare.