Originally Posted by
FBinNY
No a hanger won't help.
On a
Mixte frame, the rear brake is attached to the central stays. This avoids the cable routing issues that a seat stay mount causes. But there's never enough room for the cable so SOP if for the yoke to be looped around the seat tube as the OP described. The hanger is integrated in a bridge typically about halfway up the central stays.
Use of a hanger lets you make the straddle as long as you want, to run it past the seat tube. It's common practice on BMX freestyle bikes with U brakes mounted under the seat stays. (or, less commonly, on top of the chain stays)