Decided to play the Aedui because I'd played a bunch of eastern cavalry factions (Saka, Baktria, Hayasdan) and wanted to try out a western faction that was more focused on infantry. Turns out the joke's on me - the Aedui have quite good heavy cavalry, and I win most of my battles with my generals' bodyguards (though usually with some infantry support). Their roster seems pretty well-balanced in terms of skirmishers, heavy infantry, and cavalry. Battles were fun, though mostly of the hammer-and-anvil variety.
Difficulty-wise, I also thought this campaign was much harder than Hayasdan or Baktria (though perhaps not quite as hard as Saka). The numerous rebel armies and weak starting financial position make it a real struggle to expand effectively at first, especially as each new territory you conquer is immediately desolated by the surrounding rebel armies. I kept looking for an opportunity to come up for air and build some infrastructure, but instead I campaigned almost constantly for 100 turns, with every new conquest leading me on to further rebel enemies. As a result, though, I didn't really wage many wars against other factions in my first hundred turns. I tried to keep the peace with the Arverni, but ultimately turned on them when their armies pushed into Iberia, seizing most of the Gallic territories. My incursions into northern Italy also brought me into brief conflict with the Romans. Overall, though, I felt like the opening was suitably challenging without being overwhelming, and also enjoyably different and more claustrophobic than the wide open areas of the eastern map.
The only "balance" issue I ran into was how incredibly powerful the Romans are, both in terms of unit quality and number of units, which I imagine is mostly intentional (given how badass the Romans were). However, I note with approval the decision to decrease the power of Camillan Roman infantry at least a little bit; right now, they are far and way superior to the general Gallic rosters. The only Gallic infantry that can hope to stand up to them man-for-man for long are the elite nobles and retainers, who are much more expensive and also have a smaller unit size. That said, I'll probably go back to the Aedui or the Arverni at some later point when their reforms are worked out. Fighting the Romans (even for the little bit that I did) was a much greater challenge than anything I'd run into as Baktria or Hayasdan.
I did run into one possible issue with rebel army AI behavior. The Aedui are surrounded by powerful rebel factions, designed to slow the advance of both the player and the AI towards superpower-dom. However, I found that as the player my territory was a magnet for AI rebel armies, even ones from fairly far away. Both the Volcae (one stack) and the Ligurians (two stacks) migrated across neighboring rebel territories specifically to invade my budding Confederation. As a check on the player's expansion, I really enjoyed having all of these armies invading and desolating my territory - it greatly added to the challenge of the game. However, it also made it much easier for the other AI factions to expand rapidly, leading to some disappointing situations. For example, the Arverni conquered the territory of the Volcae with only four units, as the Volcae had sent virtually all of their forces on a long northward trek to attack me. Similarly, the Ligurians almost immediately sent two full stacks of units through Massilia's territory to attack me, which allowed the Romans to overrun all of northern Italy by turn 30 (I re-loaded and managed to grab Mediolanum and Felsina before them, the better to fight them later). Again, having rebel armies invading right and left was a very fun aspect of the campaign; however, having a player-controlled faction in western or central Europe seems to mess up the rebel AI's priorities, leaving them especially vulnerable to the ever-northward march of the Romans.
I've also begun to notice how easy it is to placate the AI with very basic diplomatic tricks, like offering them a 100-a-turn tribute for 30 turns. I offered this sort of tribute to the Romans, and as long as the tribute held, they avoided war with me. This was despite the AI's obvious desire to crush me and take my holdings in Cisapline Gaul - the Romans piled up four full stacks of soldiers just south of the border, and milled about angrily, ready to attack. However, the AI seemed unwilling to forgo a measly 100 a turn that it clearly did not need! On the one hand, this sort of tribute-spamming seems pretty easy to exploit. On the other hand, I like that tribute options seem to make the AI more responsive to diplomacy (avoiding wars, ending wars, entering alliances, mutual attack on neighbors, etc.).
One final topic for discussion - the Teutonic character system. I appreciate the concept behind this system - that the Aedui are a confederation of many different tribes and families, and that as such they do not have a single family tree. The result is a faction that plays differently from the other monarchy-based ones that I had previously played, which I appreciate. However, I also understand the frustrations that some people have directed at this system. The biggest problem is the lack of transparency concerning how it operates. With a family tree, the player can see whether new generals will soon be coming of age or not - even if no new generals will come for many dozens of turns, there is still an understanding of how new generals will appear. Currently, the Teutonic system does not have this sort of transparency. I received three new characters in my game, one from adoption and two from heroic battles. However, I could not figure out what was triggering these new characters. The size of my Confederation appeared to be only very weakly-related to the appearance of new family members; the last 25 turns or so I had 11 regions and 8 family members. Furthermore, my attempts to generate new family members through "heroic victories" generally failed (I received two new family members, despite winning a dozen or so heroic victories against AI rebel armies, while having less FM than settlements).
None of this was game-breaking, but it did become a bit frustrating by the end, largely because I had no idea whether I was doing it right or not. The transparency offered by the family tree helps alleviate some of this anxiety - no matter what you do, new family members will eventually become available, and the player can watch their progress towards adulthood even as they also receive periodic adoptions or men-of-the-hour. At the very least, the player is assured that by waiting, new family members will become available. The "Teutonic" system provides no such transparency; I was left with fewer family members than I would have liked for my expanding empire, and with a sneaking suspicion that I might never have enough family members to govern all of my settlements.
I like the use of the Teutonic system for some factions that are meant to represent confederations of smaller sub-groups, rather than unitary monarchies or republics. However, in terms of implementation, I would recommend: 1) making the incidence of new family members in the Teutonic system more responsive to the number of settlements the player controls, ideally through the rapid arrival of adoption offers when a new settlement is taken; and, 2) improving the transparency in-game of how to generate new family members under the Teutonic system, to reassure players that there are options for getting new family members.
One final note - all three of the new family members I generated received the tribal trait "Aedui" after spending a turn in a settlement. Does the Teutonic system only generate family members of the ruling clan? If I had waited longer, would it have generated more men of the Brannovaci, Carnute, or Insubre tribes (or even other tribes, like the Semenones, Pictones, or Arevaci)?