Looked at your pics some more.
I think you could easily modify your design and gain the necessary clearance to install the brake disks, and the servo/linkage.
What you need to do is make a new plate, move the chassis braces forward and backward to make room for the disks. Then you can mount the servo on the outside of the tvps and run the linkages thru the tvp transmission hole that is across from the center diff.
I am referring to this pic:
Move the square braces forward and backward and make the plate longer to gain clearance for the disks on the front and rear diff outputs.