^As long as you know your limit to how many characters you can play and keep the playercest* to a minimum, I don't see a problem with OCs coming in game. With that said, your comment makes me want to bring up a concern I do have for this game. It's something I remember happening a lot back in the old RP and I think it's worthy of bringing up here. This applies to everybody playing btw, not just you Belmont, so when I saw "you" I mean a collective "you".
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Playercest, or only playing by yourself with your characters chosen.*
While playing themselves, some members played their favorite characters and just stick with that. They would branch out sometimes when the plot called for it, but there was this thing of always going back to your favorite characters and sticking by with them. This is fine if you're just writing a fanfiction, but you're out in the open on a public forum, writing with other members that want to interact with different characters too. It's not fair for everyone else if you're hogging these characters and not reaching out to pursue the story onward. That doesn't mean shy or more introverted characters have to be OOC and reach out like how an extroverted character would, but there are ways around that while retaining your characters.
This game is all based on self-insertion. I mean heck, that should be clear from the set up coming in that's exactly what it is going to be. Just remember, at the end of the day, while you are playing yourself, it's still a character with strengths, weaknesses, quirks, and their own backstories, even if they might be reflective of your own. How my character is going to react in this set up isn't going to be reflective of me 100% of the time, especially if I'm adding an LBT history in her story.
I was guilty of playercest, taking too much of the spotlight, and other common newbie mistakes back when I was an itty, bitty rper. This RP was the first I ever ran those years ago and I've learned a lot from RPing on other different platforms since then. I also should add, this is going to be my first group RP in over a year. Since I usually RP one on one over GoogleDocs or Tumblr these days.
In short, keep in mind this is a collaborative writing activity, everybody gets their turn, and stick to the basic rules of all Role Plays.