Two idler pulleys would be ideal. One of the problems with most motorcycle drive systems is that unless the front drive sprocket is concentric with the swing arm pivot the needed length of the chain or belt that is needed changes with suspension travel. The further away from straight horizontal the loosed the drive medium (belt, chain) becomes. With an idler on either side of the swing arm pivot (above and below) the drive media length can become fixed length.
One objection to belt is that one would need to remove the swing arm to replace it. But the final drive on the VDR is topologically outside of the swingarm already. If you could get enough slack to jump a chain off the teeth of the sprockets You could remove a chain without breaking it. Same thing for a belt. This means that for a belt drive with idlers you might be able to remove and install a new belt strictly by loosening the idlers.
I read at least one analysis which indicated that chain was inherently jerky and thus we have a need for cush drives in our wheels.
This same article indicated that in terms of drive efficiency chains win by a slight margin over belts. However, a few hundred miles into your trip when some of the chain lubricant is use up the belt catches up and becomes just as efficient.
We could make chains better. A fully enclosed chain with idler tensioners would be better than a belt in every way except weight.
But since the chain is topologically outside the swingarm one can deduce that the Honda engineering was originally for a belt.