[Chris is me]

With the Nonadrive, I would say the mechanical complexity in design would be in making the pivot modules rigid enough for FRC applications. In particular, when resisting pushing a moment is applied through the modules (I think?) since the traction wheel is on a module, so the forces are transferred through the chassis via the pivot axle. It seems a lot esaier to make a standard 6wd than to make a Nonadrive. The extra weight assumes a lack of sheet metal capability and having to use thicker sideplates due to a lack of ability to add flanges among other things like that.

I would argue that Nonadrive is simpler to code because it basically takes zero programming, but basic robot centric mecanum code is not a tough challenge either.

@JesseK: I was suggesting 1 CIM + 1 FP in each of the forward wheels and then just a CIM on the side wheel since strafing is secondary to forward motion for a slide drive (if it isn't secondary, you should probably be using a holonomic chassis). With a crab module in the center I would probably suggest 2 CIMs on that and 1 CIM + FP on the outsides (off the top of my head here, not based on math or anything)