While three team trades are not common, they do happen.
Trading Mayer for KMarte improves one slot, but keeps the 3B slot open, as Mayer is no longer a 3B option.
I have no idea is PHI would send Painter to AZ for Duran, but he'd be that "controllable SP'er." Something like that might work. Maybe not.
If it wasn't for the money issue, we could just sign Bregman, Bichette or maybe Suarez, We could dump Masa and DH Duran, or trade Duran plus Crawford/Harrison/Sandoval for a #2.
There is talk of trading for Donovan, and he'd be an improvement, but I'm not sure he'd be enough or what STL wants for him. I would not give an OF'er for him.