Brian, I'd be very tempted to buy a saw over there that's nearly identical to a model that's sold over hear then order the arbor, washers & nut for the US market saw.  Then you can buy whatever 5/8" bore dado you want.  I know the restriction revolves (pun intended) around inertia and the inability for a saw to coast to a stop within a specified time, the skeletonized dado aims to reduce that inertia so a saw will coast to a stop within the required time.  I'd much rather have a heavier dado stack when plowing a large groove in white oak vs. something aiming to conform to some stupid regulation.