Agreed, the armor on the horses is a major thing. The annoying part of it is that it does not mention it on the unit description, making it difficult to evaluate the units. Same goes for some other details.

Also, I absolutely hate it when I see some 5/1 stats (att/def) on pikemen/halberdiers/whatever and it seems that they are still effective on the field. Why have unit stats shown on the unit card if comparing them yields no result over their usefulness? Why not just go back to M:TW1 style where it says "good attack" or "Very good defense" instead of numbers that make no difference.

I suppose that the issue with the building order has to do with the italian heavy cav units. The Broken Lances for Venice are indeed heavy cav that you get later from cities than feudal knights from castles, but that is just the point. The BL's you get from just teching up city walls, so they need to have high upkeep to be balanced. So far, as Venice, I have used the Broken Lances as heavy cav along with Cavalry militia simply because they are available in Italy and I have no castles in Italy. There is no balance problem there.

The dismounted men-at-arms is a bug IMO, as they really have no advantage over dismounted feudal knights. The Mounted MAA may be better than Mounted FK because of the barding on the horses though - have not really tested this one out.

I suppose that just having two nearly identical unit types with building improvements has one upside, and that is to have a bigger pool of units, but since you only have 3 recruitment slots this is not really likely to be of any help.