I think Brantley, Donaldson, Realmuto or Ramos, would be a very solid start and I think you would have retained resources to go get relief help a complementary bench player and explore a rotation upgrade at the same time.
I'd be very flexible about selling performing veterans acquisitions at the deadline if it didn't work out record wise.
I suppose there are better long term solutions and with theoretically less risk, but I am afraid it would come at a real cost to the system that most would want to avoid. But I'd probably be more willing to do that than some folks.
I don't think Atlanta should scorch earth the system to try and win right now, but there is no sense in having the best farm system forever.