I’ve been considering the same question actually, but I’ve not really thought of a good way to represent Napoleonic infantry in KoW yet…
The problem with crossbowmen with gunpowder weapons is 1) They’re absolutely God-awful in melee, to an extent which doesn’t really fit, I think; and 2) they’ve got Reload! which means you can’t advance and fire but are tied to a passive gunline approach - the antithesis of Napoleonic infantry tactics, mostly.
As for magical items, I don’t think there’s any that affect shooting anymore? You could probably represent light infantry by Brew of Haste, Wine of Elvenkind, and/or Maccwar’s Potion of the Caterpillar, so as to make them faster/more manoeuvrable, but it’d get really confusing which unit has which, and you still wouldn’t have any real option to represent grenadiers.
On a slight historical nerd note, whether or not grenadiers should have their own unit really depends on the army you’re building: the Austrians and Russians often fielded entire bataillons of them on campaign, but for the French I can only remember one instance of this happening - a division during the 1809 campaign - and for the English none at all. So maybe that way you could sidestep the problem, but then of course you also don’t have the fun of different units…
Sorry I don’t really have helpful advice here…
As for avoiding skewed lists, you could use cavalry as your melée mainstay (Knights for heavy cavalry, Mounted Sergeants and/or Scouts for light), in order to have a list that can at least survive if the enemy makes it across the battlefield and into combat, but that would require a very cav-heavy army…