Awesome design! Nice work.
Here is a similar design by 221 Robotic Systems. It's a customizable research platform, and has an interesting setup. Steering is accomplished using one motor to rotate two swerve modules. Another motor rotates the rear swerve modules. It seems as if the modules can be turned more than 360°, as the CIMs driving the wheels are located on the center of the drive train, and connect to the modules using a sprocket and chain.
http://www.team221.com/viewproduct.php?id=128
It seem very similar to your design.