I personally agree that Bulgaria, Serbia and the Pechenegs should not have the same homelands as the Hungarians, but I would deffinitely add Thrace, Macedonia, Serbia, Wallachia and Epirus as homelands to the Bulgarians - after all, we did control Wallachia immediately after the liberation from the Byzantines, and at one pint in the thirteenth century most of the Balkans. A good case can be made about Moldavia and Pannonia. But I agree, Tyrolia, Volhynia and Austria are ridiculous. What applies to the Bulgarians, applies also to the Serbians (add Croatia and take away Thrace). As for the Spanish, they did retake the Iberian so I believe their current homelands are quite reasonable. If castille and Leon are taken away from the Almohads and Almoravids, they will get no iron provinces, and they need the upgrade badly considering they get no new troop types in late and their units are obsolete throughout the entire game (their early units are useless against the bellatores and feudal men at arms, their high units are better but more suited for the early period, really, and Jihads are the only lifeline providing decent troops).
I also do not think that the Cumans should share the same homelands and troops for the most part with the Novgorodians and Russians. I think the Pechenegs should not get Germanic Mercenaries as bodyguards should they survive until the High Period, but Avar Nobles (a fictionary fantasy unit with this name, as the Avars were wiped out loooooong before the start of the game, let alone 1204, but perhaps if renamed would make some sense), and that they should be able to produce horse archers in early and Steppe Cavalry throughout the game (instead of the Hungarian and Balkan troops).
There are also a few glitches that need fixing - switching the Pechenegs to pagans (they were anything but Catholics, and it is funny when the Pope intervenes on their behalf against the Hungarians or Poles), the Serbs to Orthodox, and the Cumans cannot produce ships, which is a bug (and effectively renders them defenseless against the superior Byzantines). Every faction seems to be able to produce Teutonic Order troops in high, which I admit I have been taking advantage of (those order sergeants come in handy against the Horde), but which I should try to fix.
Finally, I like that even the simplest troops, with few exceptions, take a lot of buildings and upgrades to produce, and that ships cannot be produced everywhere and linked to cover the entire map. I feel that the Catholics get a huge advantage by being able to build barques everywhere, and the Crusading factions get a huge advatage when it comes to homelands, but the AI does not seem to ever take advantage of this (but the Sicilians usually ravage through North Africa getting huge quantities of the Muslim troop types they are allowed to build).