[Lil' Lavery]

Simply put, my question is... why?

I can understand possibly adding a set of 3rd wheels in the middle between the mecanums for helping stability (assuming they're all coplanar), but 10-wheels is excessive.

More wheels doesn't equate to more traction (or more pushing power).

The most glaring flaw of all is that those big, heavy, expensive mecanum wheels are nothing but giant, efficiency (and "pushing power") robbing wheels in this drive system.
You have each side linked via chain, meaning each side of the drive train acts as one. In order to get strafing motion out of mecanum wheels, you need for each to be independently powered. In this configuration, each mecanum wheel is diverting some of your force in unused directions, costing you pushing power without giving you the maneuverability advantages.