John,
There may be others out there who can answer this better but going from manual to auto isn't as simple as swapping in a TC. I will take a stab at it with my small arsenal of info on the subject and maybe someone else can fill in the gaps (or correct the errors).
The reason a TC works in an auto box is the gear set. They are planetary gears, meaning they are ALWAYS engaged and the ratios are changed by allowing different portions of the gearset to turn or remain fixed relative to each other or the gearbox. This is what all the clutch bands do and is why your box won't shift correctly if your bands are slipping.
In the manual box, the individual speeds are always engaged but the collars locking the gears together are free spinning until the shift fork locks them to the output shaft. This is a little difficult for me to describe succinctly but I am certain someone else could probably do it better.
Where this is all going is with the TC, the engine is always spinning the input shaft and it only "disengages" once the motor is below its stall speed. Disengagement is not a completely correct description as there is probably too much residual fluid friction for the input shaft to truly be idled and would likely continue to be spinning at whatever RPM the motor is running. This would not make for very smooth shifting of gears in a synchro-based box.
For a manual, the clutch physically disconnects the motor from the box and as the shift fork engages the locking collar for the selected gearset, the synchros get everything to match speeds before they click together at whatever road speed the vehicle is traveling. Leads to nice smooth shifts and easy on the drivetrain.
The interesting concept going through my mind now though would be a TC-equipped "dog box." The dog box style gearboxes have relatively enormous lobes (compared to synchros) which enable them to be shifted without using the clutch. You simply lift off the gas to relieve the pressure on the dogs and slam the shifter from gear to gear and the large, strong dog ear-shaped lobes engage the desired raios at will (at least that's what I understand, never having driven one). I'm not sure if you have to match revs to downshift, but I imagine it'd be pretty awkward if you didn't. It's much more of a competition box and I'm pretty certain the dogs don't exactly have a warranty or a 100k mile life expectancy...
Where this thought is going though is possibly with a dog box, the TC would let you idle and shift as well. Not too sure how it'd really work though but it'd be really interesting. You would likely need to always have a gear engaged though as if you went from unrestrained idle to selecting first gear it might get expensive quickly.
Anybody have any experience out there?
Chris