Just regarding 3 (Historical Victory Conditions):

What a faction did and what a faction may have liked to do are two different things. That French Crusaders conquered Constantinople to me would suggest that English Crusaders doing the same would be very reasonable. Whether that means it should be a goal for the English (or the French for that matter)...

Goals for a faction should be inspired by history, but mainly drawn from the historical situation as it was when M2TW starts (i.e. what may have happened after then is not so relevant). However these goals should also encourage an enjoyable game - shaping both the player and the AI's actions.

I must say I quite liked the GA system in MTW (although of course it could be improved), especially how conquering new lands or defending your existing ones had different degrees of importance for different factions.