Some benefits of pairing swerve modules would be:
* Ability to drive (2) swerves with (3) CIMS
* Easier to add gear shift
But, what kind of drive action/control are you seeking: Crab or Snake? Either could be accomplished through pairing, but not both together.
For example of crab & snake, see:
http://www.chiefdelphi.com/media/papers/2400
http://www.chiefdelphi.com/media/papers/2401