Gonna take a guess that plugins will be disallowed since it'll turn openRCT2% from "who can click the fastest" to "who can make/use the best speedrun plugins" (though to be honest watching a speedrun like that might be interesting as its own thing). They aren't included in the stable build of OpenRCT2 yet, but once they are it might be a good time to add a caveat to the rules mentioning them.

That's a good suggestion, thanks for that. I'll add that to the rules soon. I'd love to see some TAS runs of RCT2 though, I agree that they'd be pretty interesting to watch.