Well, my thought here (after I made that post, when I made the actual updates) was that a light armor could be something you graduate out of. A starting duelist uses light armor because it's simply better. You get more AC out of it, and it doesn't restrict you horribly. As you gain levels in duelist, you eventually grow out of it, as your other bonuses and abilities outscale it.I would go further with this than you already have. As it is, a Duelist in light armor is just strictly worse than a Duelist in no armor. The light armor wearer has a bit more AC but loses many of the Duelists coolest abilities. Make it a more even trade.
That said, what abilities don't work in light armor aside from Fancy Footwork and the initiative bonus? For example, penetrating strike and challenge don't have any armor restrictions. I could maybe give a reduced initiative bonus to a duelist with light armor, but I can't think of any way to reduce the benefit of fancy footwork for someone in light armor while keeping it meaningful. Or would you suggest just making that fully available, and the only difference between light armor and no armor being the AC and initiative numbers?
-No longer requires Mobility as a prerequisite.
-Elaborate Parry now explicitly requires no armor for the full bonus (upon rereading I realized I hadn't specified this, so it could have been interpreted as someone could take this class and wear heavy armor and still get the full +level AC bonus, which was not intended)