Aha! I've just had another idea, and feel really stupid for not thinking of it in the first places, my normal work is obviously draining my brain.
Essentially, similar to the from beam ends on your original sketch, the beam forks with the top fork extending upwards. An additional arm would branch off forwards or backwards, and then a very light simple upright would mount to these three point via some Shim mounted BJ's. Still fairly bulky but...less aero disturbance and less complicated (calling it more elegant would be a push, no?)
EDIT- Three roughly evenly space branches (2 mottom one top) might end up more optimal, depending on loads and packaging issues for caliper mounts, provided you are mounting brakes outboard that is.