For the Hungarian units, perhaps just take the NTW approach and give the Austrians two sets of units? Austrian/Hungarian Line, Grenadiers, etc.?
I agree.

We may just end up removing the ability of dragoons to shoot altogether...or perhaps have a 'late dragoon' unit which acts as medium cavalry, but is no longer armed with a carbine. I think that dragoons as mounted infantry pretty much dissapeared by the the mid-1700's, right?
I would remove ability to shoot from medium and heavy cavalry altogether and give it to the light cavalry. Although there probably were some instances of battle cavalry using their firearms in volley fire (this is true even for the napoleonic periods), main emphasis was at rapid charge with cold steel. Although all prussian cavalry were taught skirmishing drill (even cuirassiers), it was meant only for outpost duty.

The idea with "late dragoons" is sound. ETW period is the time of gradual evolution from "almost 30YW tactics" to the "almost napoleonic tactics". I am no expert on Great northern war or any early 18 century conflicts, but i can see greater prevalence of cavalry fire (as a remnant of caracolle tactic) in the first half of the century.

So, perhaps we should Establish Austrian infantry as our 'baseline' average infantry? Give them the nice, round, stats and even price/upkeep, and judge other countries infantry stats as 'better' or 'worse' than theirs? That might make things a bit easier on the stats front.
Yeah, we would need some baseline to compare to. But we would need to take into account the effect of technology on the performance of combatants. For example ramrods (which are sadly missing from ETW technology tree) and the advantage of the prussian infantry (silesian wars period) equipped with iron ramrods against austrians with ramrods made form (easily breakable) wood.