I'd be rather inclined to say that an auto gearbox with a clutch would be the best of both worlds - the torque converter is the hydraulic pump to power the auto gearbox, but at the same it's also a "fluid clutch", of sorts - this is a VERY rough comparison, but think of a tube - a turbine at one end, a turbine at the other - the turbine on one end is forcing fluid down the tube, forcing the other one to spin. If you hold the other turbine still (or slow it down forcefully - i.e. when the auto gearbox shifts) the torque on it increases (hence, torque converter), but it doesn't stop the turbine at the other end completely.
However, as you can imagine, if the unpowered turbine has a load put on it, it'll never spin as fast as the turbine on the other end, no matter how efficient the turbine is. This is the major drawback of the auto gearbox setup, and why it's slower than a manual - nothing to do with gears, they still use the normal cogs - it's just the torque converter.
Anyhoodles, I know this paddle-shift idea is pointless, but it's not very often you have fun doing something that does have a point, is it? :-D
At the moment I just want to do it to basically shift gears - i.e. fully depress clutch as fast as possible, move gearlever, release clutch (Can do automatic throttle release later, but I'll get to that later).
However, this "smooth shift" idea has got me thinking - if I can find out the exact gear ratios, I can dynamically calculate what speed the engine will spin at what road speed - so I can make it change gear, and keep the clutch depressed until exactly the right moment, when the engine is coming close to the speed it will be spinning when the clutch is let out, and then release the clutch - not suddenly though, sort of like a slow-ish let-out. Later on, if automatic throttle control can be managed, the throttle can be released when the shifting starts, and slowly regained as the clutch is left out.
which brings me to something else - if the synchros on the gearbox go bust it can be programmed to double-clutch
Some good ideas floating around here... though I'm afraid this project will be in the planning stage for a while yet - one of my close friends is hopefully coming to visit from the other side of the world, and the obligatory tour of the country might turn out to be, well, expensive
Now I have a problem though - got to find some kind of high-speed pneumatic-or-otherwise actuators that can be controlled by digital electronics. If I can find those, this battle is half won!