Easy!
As part of my senior capstone design project at Kettering University, I was permitted to use a mecanum-wheeled drivetrain that 862 had lying around.
(It was originally the base of our 2008
FIRST Overdrive robot, "Thor", which had long since been harvested for parts; there's talk of restoring that one next, after we finish our current project of refurbishing our '09 bot.)
Anyways, here's what it looks like now:

(click for video)