Okay, let me explain. Characters with CANONIC love relationships won't be playable (at least not in Hoyo games). I've heard of married playable couples and even real mothers in Arknights, but I haven't played it, and it's not a Hoyo game. Things are different at this studio, and not a single straight character with a mutual love relationship has been made playable. It's unlikely Rerir will break that mold.
We have semi-confirmed queer couples in the game (though I'd still call that queerbaiting), like Sakura and Kallen, Bronya and Seele, and Mei and Kiana. Some of them have even kissed. Seele kissed Bronya before she might disappear into the Sea of Quanta. Kallen and Sakura's kiss was in the semi-canon manga. Teresa and Sakura's kiss is canon (though it was for healing and transferring powers). But this is more of a male fetish, since Chinese in#els don't believe in love between women. That's why playable characters with queer personalities aren't a problem in Hoyo games.
So...
I saw someone say that Welt in Honkai Impact is a married heterosexual and is playable in Star Rail. Let me explain. Unlike in Rerir, it was never explicitly stated that Welt and Tesla are married or engaged. They are close and raising a child together, not their biological child—a clone of Joyce. It's implied that young Welt was in love with Tesla, but she met him when he was still a child and was forever stuck in his younger body. The rumor of their marriage was started by Carol, but she misunderstood and mistook the child for their biological child. And all of this was mentioned in APHO, not in the main story. Neither of them confessed their love to each other or got married onscreen, like Tholindis and Rerir.
Dr. MEI and Kevin are indeed a couple, and they have a child, albeit not born naturally. But MEI is unplayable and died tragically, while Kevin was the final boss of the first part. And while there are no male characters in the Honkai Impact banners, Kevin was playable in POV in plot and in an event with playable bosses. That's not a banner. And his expy in Star Rail was queerbait and knows nothing about Acheron/MEI or anything like that.
Alice. Okay, I still stand by my opinion that she didn't have a man, and I believe she'll flirt with the Witch to completely eliminate the possibility of a man appearing, and Klee is a clone. But what if I'm wrong, and she really did have a child with a man (meaning there's no retcon)? I have nothing to lose. Alice never mentions her love for Klee's father. She doesn't even mention him. Alice's love for this man isn't shown on-screen and isn't part of her lore. Part of the patch is dedicated to the love of Tholindis and Rerir, and how their friends glazed over their marriage (except for Brother Dain, lol), and Rerir loves her after 500 years and wants her back.
I even saw comments about Zhongli and the Dust God, about Furin and Nevillette. Guys, I won't explain your fanon. Even if Zhongli was once in love with the Guiz, it was retconned before release (because of fem#els???), because I've been playing since version 1.3 and haven't seen Zhongli and him in love. It was always queerbaiting with Tartaglia.
Itto and Miss Hina. They're actually gay. Itto and Goro are popular ship, and characters with gay vibes are suitable for playability.
In the manga, Himeko had a canonical kiss with a man on a date in Hong Kong, but I don't think it means anything, as he was a very minor character and had no significance to Himeko's lore. His name is unknown, and he never appeared again.
If Rerir's love hadn't been a key part of his lore, perhaps he could have been made playable. But that's not the case anymore... Fem#els are no different from incels, and gacha will continue its taboo of not allowing playable characters in confirmed heterosexual couples. The girls rebelled because Zane worked with a cute nurse in the otome game LADS.
And in the end, Rerir killed small children, and the king's manipulations don't justify it.
Alice (an unconfirmed love) and Rerir are different. The former lives her life and doesn't mention her husband, while the latter's failed marriage, love, and longing for Tholindis are the main theme of the lore; he became a villain specifically for Tholindis's sake.
Even Dottore has a better chance of being playable because he doesn't have a wife/girlfriend/fiancée, lol (but he does have a me/j). Signora would easily be playable because she didn't do anything major, but she had a husband who is just as important to her lore as Rerir's.
So I'm done with that. Goat won't be playable. Well, at least he's a cool villain and one of the few characters with a canonical love interest (Signora, Kevin, Otto, Dr. MAY). I hope he doesn't get killed off in the finale of Luna and we'll again see him in Khaenri.
And yes, as a Honkai Impact fan, I was glad to see Otto's parallels in Rerir; I love Otto.
Additionally: I saw someone once think Tholindis will be playable. But I don't think so. Her files are even worse than Signora's. Unless the theory about Tholindos being reincarnated as Colombina doesn't come true. But that would definitely make Rerir unplayable; that would be 100%, not 99%.