I totally support this approach with just one little notion,

If a solid in Moi would have a single style assigned to it - I would go and assign a material to a group in Sketchup. If multiple materials are assigned to different parts of a solid in MoI - then I'd assign a material to each respective geometry part inside a group in SU

I personally always on purpose model solids as one style and if i get a group which has a mat assigned to geometry inside of a group in case of a multifaceted solid - I'd have to manually repaint each and every facet if i need to change a mat.

(of course there are plug-ins in SU - but that's not a neat way but a workaround)

No matter how you do eventually implement the feature I'm already happy as it's already looks like a good upgrade for me))

Thanks
Igor