[DWThomas]

What about using something like an remote control car transmitter and servo...

Yes, I think in the past an approximation of this topic has come up and the radio gear and servos for model cars/boats/planes have been suggested. If you really wanted to add handling for T vs B and precision controlled exposures, some sort of micro-controller based enhancement added to such gear might be the way to go. A decade or two back this would have been right up my alley, but since retiring I confess to having become rather slothful these days (unless I suddenly find I "need" one).