It could be an interesting AU and there’d be some really fun things to explore, especially as we see Mace is someone who also struggled with righteous anger, which would have been an interesting parallel to Anakin. But there are two reasons I don’t think it would have changed anything: 1. One of the biggest themes of Star Wars is choice.
(George Lucas interviews, edited by Sally Kline) This means that it doesn’t matter who Anakin’s teacher was, that it still ultimately comes down to that Anakin’s choices were his own. There can be external influences and opportunities that Anakin might not have otherwise had, there can be some responsibility placed on Anakin’s choices from those, but at the very, very heart of it, it had to be Anakin’s choice and no one else’s. Saying that another teacher would have kept him from falling to the dark is saying that Anakin’s choices weren’t what decided his fate, but instead that he had no actual agency as a character and instead it was all about what other people did, that his own choices didn’t matter, because it was Obi-Wan’s fault somehow. 2. For all that there’s a similar vibe between Obi-Wan & Anakin vs Mace & Anakin (the banter they each tease each other with), I actually think Obi-Wan was the best possible teacher for Anakin. What Anakin needed was structure, but he also rejected structure because he didn’t really want to listen to it. What Anakin needed was a strong hand to guide him, to make him sit down and self-examine, but he also rejected any attempts to make him do so, because he didn’t really want to listen to it. That’s the thing about Anakin, he had incredibly strong ideas of what he did and didn’t want and nobody could actually physically make him do anything he didn’t want to do, they could only ask it of him and Anakin decided whether or not to listen. So here’s what any teacher of Anakin’s would be facing: Someone who desperately wanted all the love in the galaxy to be poured into him, but someone who would not actually benefit from that. Padme did that and he still turned on her just as easily as anyone else, after all. They’re also facing someone who desperately wanted structure and an authority figure, but would reject it because he didn’t want to admit to what that said about him and how much he wanted it as an all-consuming thing, not a healthy set of boundaries between himself and the person he cared about. No other character could have walked the line between loving Anakin and being strict with him as well as Obi-Wan could have. No other character could have found a line between getting on his case when he needed it in a way he could accept it and actually talking to him about it. Obi-Wan is the character who actually initiates conversations the most in the story, other characters (like Qui-Gon or Mace and certainly Anakin himself) do not do this nearly as much. Obi-Wan is the character who finds the best balance between “I understand why you’re reacting this way” vs “You still need to stop it”, he’s the one who best found the line between the unhealthy attachment Anakin was seeking vs a more balanced love that Anakin could still accept and would want to do as Obi-Wan asked, because they loved each other. Obi-Wan and Anakin complement each other in a way that I’m not sure any other pairing would have done, because they’re either too different or too similar and Anakin would have rejected them. Like, Anakin’s not a puzzle to solve that has one key answer that will unlock the whole thing, he’s not someone who made choices based on other people. Anakin had his own personality and his own strong opinions on things, those don’t just magically go away because he had a different teacher. So, you have to navigate the waters of Anakin’s character, who he would have bonded with, who he would have loved, who he would have responded well to–not just what he wanted, but what he actually needed and how much of that he would have actually accepted and listened to–and I think Obi-Wan was the one that was best meant to teach him, the one who could inspire Anakin to want to listen to him, while also seeing him objectively, and actually communicating with him in a way Anakin would respond to. Can you imagine anyone else that Anakin would have a fight with? Obi-Wan de-escalates situations, and I’m not sure Mace or, say, Qui-Gon would have done the same. Qui-Gon, as Master & Apprentice showed us, was not someone to de-escalate a fight like that–he repeatedly doesn’t actually talk to Obi-Wan about things that he knows he needs to, he shuts down conversations that he gets angry about, etc. In The Phantom Menace can you IMAGINE him doing this to ANAKIN??
Mace I think would be too reserved for Anakin’s liking (in as much as he can be incredibly warm at times, I don’t think it would have been enough to win Anakin’s loyalty, this doesn’t make either of them bad, just not a good fit. They do have some good moments, Anakin laughs when Mace praises Artoo’s heroics and says he sees why Anakin trusts him, and I do think there would have been some interesting conversations about anger to be had, especially considering Mace’s own history with it:
I like the idea of Mace and Anakin, I think it’d be an amazing exploration and he is at least up there (well, it can never be a long list because we don’t actually know that many Jedi), but I don’t think he would have had enough warmth in Anakin’s point of view to overcome Anakin’s mistrust. And the only other person I’m reasonably willing to entertain that might have been able to be a good match for Anakin would have been Yoda and even then I think Anakin really needed someone he felt more personally loyal to, in a way that I think Yoda’s boundaries might not have allowed for. And that doesn’t make Yoda bad, only that I think finding the fine line to walk between Anakin’s desire for structure versus his desire to have someone be soft on him, was pretty difficult to find.
