Ah, Naselus to the rescue again, thanks so much
I've done a little bit of testing since I asked the questions, and it seems to me that high recon in high numbers leads to faster occupation, and definitely forts slow it down (I occupied a number of provinces with different force types at the same starting date, by unloading them all from a ship). Therefor in this instance Hussars do have some use, as faster occupiers than any other troop-type besides aeroplanes. With a base recon 1 point higher than cavalry, and 2 points higher than cuirassiers and dragoons, I'm not sure if I would call them useless. In fact, I'd recommend for occupations armies of 3-5 cavalry, hussars, or aeroplanes, depending on your technology; to avoid attrition (which hurts soldier pops) once an enemy army is irrelevant (occupied fighting your large armies, blocked from a region by water/blockade, or completely obliterated).
Is there an argument why this is not as good as I perceive? I only ask because, it seems to me my logic above is correct, but Naselus says hussars are useless so they probably are!