Should probably direct comments to this thread: Plugin Hosting as it was started by a moderator and has a lot to do with this.
@JessHilario
As for private plugins, most games that use the official repo system also allow private plugins to run, they just won’t be as secure, and you may lose some users if they think they’re client is in danger of receiving malicious code. So using an official repo would not generally interfere with private plugins, but players would need to install them manually, as the client wouldn’t want to auto-install unvalidated plugins.