pic: Concentric Shifting Transmission Concept

[Kevin Sevcik]

That's a neat idea, and actually rather similar to the ball-lock trannies that started showing up a few years ago.

Example here

The main difference obviously being your use spring loaded pins. While the pins would probably cary more torque, I'd be worried that the would bind and wouldn't release when you wanted them to. You could solve that with a tapered hole and tapered pin such that the pin would get forced downwards without something pushing it up from underneath, though. Which would basically make it like the ball-lock trannies.