Well, drove home with it off and drove back to work with it off today...not one instance of shuddering. There's a *tiny* bit of clutch slip on takeoff, but that I would expect (same as any manual car)...and it's *GREATLY* reduced from when I have the TCS enabled.
My theory is thus: one of the factors used in determining whether TCS should be engaged is the resistance on the drive shaft. When there's far less resistance than the computer thinks it should have, it engages the TCS to even it out. I'm using lighter wheels (21lbs as opposed to 32lbs stock wheels), so maybe I'm more at risk since there's already less resistance. Maybe I'm passed the tolerance of the computer and so the computer thinks the TCS should be engaged. This all makes sense since the shuddering *does* feel like it's being created artificially by the TCS.
Also, the TCS doesn't just use the ABS to control tire movement. Traction Control can encompass more than just sitting on ice and revving the engine. It controls tire movement through the use of the braking, torque vectoring, fly-by-wire fuel management, and good old-fashioned clutch control. That means when it thinks the tire is slipping it might employ the brakes, it might put more torque on the opposing side, and/or it might cut the engine a bit and disengage the clutch to some degree.
All of those factors together can easily account for shuddering. It's just amazing that not a single Ford engineer has figured this out before now. Good thing I have a phone call with a corporate engineer tomorrow :) Hope he know more about dry concentric dual-clutch transmissions than the last one.