With Catherine de Medici, having Richelieu for France would be stupid. He was a great administrator that laid a great secret network in all the kingdom, having a bonus to espionage would be a no-brainer for him, but double with CdM. In fact, I would have prefered Richilieu over CdM in the first place; not because she's a woman, but because he's a priest with possibilities of fantastic hats, and we don't have any fantastic hats.
You're right, but when people talk about Gauls, I don't think they talk about the specific subcultural group of true Gauls. They talked about the Celtic tribes that were globally on the current French territory and that were the target of Cesar during the Gallic Wars. They would put in it the Aquitainii, the Helvetes, the Belgian (Cesar himself said "from all the Gauls, the Belgians are the bravest" so, for a lot of people, Belgian are Gauls) altogether, making it like they were all united, which is wrong, absolutely wrong, there never was a political, even loosely, unity between Gauls, except maybe during the Gallic Wars but, again, they lost. So, why, among all the Celtic tribes, requesting the Gauls? What makes them so different to be worthy of an inclusion besides all the other tribes? I saw all the fan mods making Gauls a civ, and I saw that it was always an horrible mish-mash.
Plus, which leader would we have? Vercengetorix? Please, another militaristic civ, a led by a guy known for loosing against Cesar? I would be pathetic. People criticized Kristina enough because she abdicated, why would you think about a leader which the best and pretty much only well documented historical moment was loosing?
This. In France, Gauls are held as a nationalistic legacy, upon which France has been built (nos ancêtres les Gaulois...). It's a symbol most often used by the right-wing (and I don't speak about the harmless royalist right-wing not able enough to agree upon who is the true heir of the Throne of France, but the kind of right-wing that would vote for Trump if they were Americans). It's despicable. And the worst thing is that a lot of people don't even realize it. All French people have red Astérix, it's our national hero, and it's, of course, full of lies and historical inaccuracies. But the fact is that a lot of people thought the Gauls were united which is, once again, utterly wrong and untrue. Making a civ on them would be silly and utter nonsense because they never manage to do anything as a united group. In fact, Gauls are perfectly represented in the game as the tribal villages: full of resources, of wealth, of treasures, both intellectual, material and spiritual, but they would still be tribes that are not worthy of a civilization. If we began to make every subcultural celtic group into a civilization, what do you decide is worthy of an inclusion? Why not the Ibers? Why not the Aquitainii? Why not the Basques (wait, no, the Basques would be awesome)? Again, we have to make choices, and Gauls, by the innacuracies people have towards them, by the lies vehiculated towards them and by the fact that they never, ever have been united, are unworthy of being represented as a civ when we have so much more countries, people or nations that are waiting in line to be represented, inside or outside of Europe (especially when you already have France occupying the same territory and Scotland representing the "celtic" blob).
Edit: sorry about the rant, but I had so many discussions and arguments with friends and foes about the Gauls that having some people helding them in high esteem while, in my country, they're so much used as a tool from the alt-right to push nationalistic anti-immigration anti-EU and borderline fascist agendas, is kind of a trigger for me. I'll stop talking about it from now.