Hey Ben,
I think Mike is correct in suggesting the ride would be very rough, unless you integrate cushion for the bolt assembly, restraining your Hiem Joint system. The body-bolt would take all the inner force, without some sort of cushion / shock absorber, to the body mount.
Without the flexibility of Urethane, rubber, (**or a dual spring cushion**), every time your wheel left the ground and slammed back down, the body mounts would take a direct hit, because of the forced geometry.
Because there is little deflection to work with on our frames, one would have to allow the force of hard cornering, so as to move towards the center of the car, and have strong memory , so it comes right back in-line.
Like mini-struts, with adjustable spring rate, to limit inner movement, back and forth, these rods would slide through the bearing / swivel. This hole would need to be bushed, or greased, in order to allow the rod smooth movement through the swivel block.
The links would be longer, so as to run through the swivel body mount, and have extra length for springs on both the inner and the outer side of the swivel. A simple pin and washer would hold the pre-loaded springs, centering the link, from either outer or inner movement. Threaded adjustments would be even sweeter, but not necessary, if cost prohibitive.
I have in mind, a solid aluminum piece, which hangs aluminum links below the body mount.
One would use the OEM bolt and urethane bushing for the body mount, and the link would hang below and run through the swivel mount, lowering and improving geometry. This aluminum swivel, could have Fafner bearings or Teflon / Nylon swivel, instead of the Hiem Joint at the body. One could still use the Hiems at both hub mounts.
The chunk hanging below the body mount would have adjustable springs, absorbing force, on both sides of the link.
The travel would be more like a Baha full link, if the geometry at the trailing arm can be twinned, so the wheel stays parallel in both directions of movement.
Now you have "x" movement at the Hiems, on either side of the hub and "X-Y" movement with adjust-ability and shock control, at the body mount. The springs would have to be tough, so they take shock and return to center.
The rear trailing arm may be redesigned to incorporate a duel trailing arm system, so the allowed travel remains parallel to the swiveling link arms, while maintaining correct geometry. (Unlike the poor control of the existing trailing arm).
I don't have a hub in hand, so as to imagine how a parallel trailing arm would be designed, or mount to existing body mounts. Maybe the same trailing arm would work, if the spring tension at the links is enough to retain geometry?