Here comes another stab following the above feedback, and using available hardware.
Pic 1: Revised schematic.
Pic 2: Note the QD male with checkvalve installed on the t near the wing inflator. Offboard bailout or Oxygen are connecyed here.
Pic 3: Close up showing the t and BOV hose with a shut-off on both the BOV and ADV.
Pic 4: Onboard O2 connected to system for OC access (this hose normally connected to left CL man-ad).
Much lighter and simpler

.
More comment/critique invited before further small refinements and cleaning.