More a subject for general Tech but when it comes to the rear hubs, syncro ones get a right hard time so let's start here. Clive kindly leant me a "suspect" hub ages ago for inspection and assessment but on the face of it there's nothing much wrong, which sewed the seed of this idea:
Why persist with the ball/roller bearing combination at all? VW only did it because it was quick and cheap to assemble and fitted the bill for a 1-ton commercial in the early 70's in the T2.
Why not evolve the concept to a pair of opposed taper roller bearings with a solid spacer and shimmed to set the preload? It would only be borrowing the idea from big "quality" vehicles with IRS of the same period like Jag XJ6's and Rover P6's, both of which used this bearing support method to good effect. Collapsible spacers were also tried later on but are not an option for offroading (cheaper and quicker assembly but shorter life, as the preload falls off with use)
Seems blindingly obvious to me but I may have missed something?
The hub nut will still need to be done up pretty tight but that's another argument entirely...