this is a post i randomly was writing about on twitter but i do think the absence of the other ocs at rad blast was an intentional decision done to preserve the core themes of vivid bad squad, to keep this a Vivid Bad Squad event in all its glory. i understand it is also a very controversial one though, because it's sad to imagine that the other members of the cast didn't show up to such a pivotal narrative moment...
thematically, rad blast and rad weekend only succeeded because of the Town... the people who live in vivid street (an isolated and unique community) put their feelings into it because of nagi and the resolve to surpass it and to carry her dream along. the problem is that literally nobody outside of the town is like... connected to any of this stuff
this is why ken's plan guiding VBS to rad blast spends 2 events targeting them. because they reignite the town with akito, and anhane's battle in WTWG gets the old folks in town to believe in them again. if everyone just invited their friends and family who knew little to nothing about the cultural stuff going on here, it doesn't really hit the same... those feelings to go beyond just aren't there. it's just a cool event to those guys
it would also really distract from the existent vbs faceless that get mentioned often in the event. during kohane's little time freeze, she calls out the lady from the crepes store--a deliberate reference to kick it up a notch, where kohane meets with the crepes shop lady with an. stuff like that is constant. it's designed to create an overarching communal feel, where they give features to what would otherwise be generics like "individual A"
i think the other ocs being there would really distract from this. nobody's going to really care and point "holy shit its the livehouse manager thats been mentioned in events since vivid old tale" except for the most diehard vbs fans who really pay attention to this grand, overarching story
as for the rui-vbs wedding1 thing. i chalk that up to earlygame VBS not having these narrative themes and the writing team not really having a gameplan for what they wanted to do yet. did you know the kotaki siblings didn't exist yet. nagi wasn't a real character until nearly 1.5 years into the game (though mentioned by name just after the 1st)
also like imagine them just watching like kotaro/tatsuya+ever and arata lol. they would not gaf