The reason covenants seem to have similar cultures is the insistence in the fanbase that all of the books happen simultaneously on a single world. This means that when you write each tribunal book, you need to write as if the players may want to put a covenant there, and in the early books particularly you can check off "This is a young rival. This is an older bully covenant you can't just destroy." and so on. This is why when you look at the early Tibunals, you can see there are some covenants filling particular roles. This means when you look at Mythic Europe as a whole, covenants tend to live in a particular way, but really that's because you are seeing a basic set of plot hooks used several times.
Really -your- covenant should not look like the ones in the book. Your covenant should look like something out of Italo Calvino. The thing is that a lot of groups don't want the covenants which they visit to look odd. I recall some blowback from the covenant which looks like a giant stone sundew flower, for example.
Changes I'd like:
I don't see the point of Characteristics. I think a Willpower stat's bot a great idea, unless I'm misunderstanding its use, because function in, say, horror games, is to allow the GM to force the player to admit the character is scared, and take control of the character's mind from the player. Then again, I don't like an Int or a Dex stat either. Magi: we get it: you are clever. I'm not sure we need a stat for that when we have the Virtue system and you can trade stats for virtue points (a little known rule) Stats are virtues pretending to be something else. I'd like instead for you to pick your VandF and have each one reflected in how you look, move or act, so that you have a frame for your character from your mechanics. Not just Int +3 (add one word description here).
I'd like each Tribunal book to live in its own little world, preferably with genre support. I like the horror chapter at the end of Transylvania, and I'd like to have something similar in each Tribunal. Transylvania gets it because you as the buyer hear "Transylvania" and you may think something like movie Transylvania, which is nothing like real Transylvania, so we need to bridge the gap, but I think we'd have done better to say "Normandy: Theme is Hermetic Chivalry" and really hammer the fun things that could be done with the idea home.
I'd move the Tribunal boundaries so they aren't obviously a Diplomacy map. Normandy and Stonehenge should be in the same Tribunal, for example. I think that's a lot more interesting than where the border is now, and it makes more use of the fact that the King of England speaks Norman French, as does his whole court.
I'd remove at least one and possibly two of the British Isles Tribunals. They exist because the people who drew the map wanted ot play there, and so they have small tribunals, but they didn't play in the Rhineland or Levant, so they are comparatively huge. I think it would be a lot more interesting, if, say, Loch Leagan and Hibernia were a single Tribunal which centred on magi in the Hebredies. I mean Argyll's technically not even in Scotland in 1220...it's lord does homage to the King of Norway.
Alternatively, I'd cut up the Rhineland more.
I'd take the Greeks seriously in the Order's history, and move at least two houses to Greece. Guernicus and Jerbiton by preference.
I'd change auras so they give bonuses for themed things, like say, storm magic or healing magic, rather than all magic generically.
I'd redo Wales. Has anyone noticed we have ignorted Wales because that's where Blackthorn is, and you'd be mad to live near them, because basically the make Wales into Mordor?
I want at least one book which is just Sicily and the Holy Roman Emporer. Seriously, we need to do Italy again, and how. If we are doing different time periods, City and Guild is basically a Renaissance Venice of Genoa book.
I'd get rid of A&A: it's a great book, but it's the big book of "Timothy, you can't do that." when I'm writing, and if I keep stubbing my toes on it, new authors will have the same and worse. Also, it prevents the characters ever discovering something new on a cosmological level if you take it as Canon. I personally hate the idea that anyone's game is Canon, although I know many of you disagree, but there really shouldn't be a book telling me why I can't make a firearm (even though the Chinese have them in 1220), or why I can't discover the Earth goes about the sun (even though some ancient Greeks had worked it out), -unless- there's a pretty clear statement that if I want to have fun, then there's no actual reason I can't and canon be darned.
I have this idea for a game based on the founding of the Royal Society, so I can see time period books...the idea they should all be linked isn't something I'd favor, though.