I would much prefer we sign a FA closer than again raid a depleted farm system to trade for one in July. And while I too would prefer Jansen, I do think most of Chapman's vulnerability in the playoffs came from the way Joe handled him. I'd be thrilled to see him re-signed.
I know Theo doesn't like to spend on relief pitchers, but priority #1, to me, should be trying to build a lights-out bullpen next season - it's a huge factor in the postseason.