Thumbstick/joystick for gaming

I'm currently designing a hot-swap hub+spoke keyboard, and I'm thinking a little ahead about the gaming keyboard module. I'm considering using a thumbstick instead of what would be the WASD cluster, alongside ample surrounding keys for RTS and other such games that have big hotkey configs.

Has anyone done this, and what has been your experience? Is it worthwhile pursuing? I've seen trackpoints for mice, but I'm not aiming [heh] to replace my mouse - only the WASD cluster. A trackpoint also seems like it could be a poor fit for movement controls.

My main concern is the height of the thumbstick: I'm probably looking at a significant height difference between the keys and the thumbstick (which I picture being pretty bad for ergonomics). Any suggestions for that would be appreciated.

Thanks!