I was able to switch the controls at some point between Tank and Arcade drive. I forgot how I did it, though
Let me dig up my code and see what I changed - I know I modified it to work with the Logitech joystick with a yaw axis.
OSRF has not yet attempted modeling a mecanum drive setup for an FRC robot, but we're excited that teams are trying things like this. If you pull it off, and it continues to run in real-time, let us know! This would be great to share with the community.