Just realised we can shamelessly scrape things from popular media. (e.g. indiana jones stream, sherlock stream, sitcom stream)
You could probably make an entire superhero arc. Custom assets would be nice.
#antihero/superhero/supervillain stream
autumn ferry
heady heart
Maybe they have to team up against vedal or another vtuber. Could work as a roleplay stream, or a twin theme stream. Animators would be eating well
(The neuro card game and neuro adventures would probably benefit from this too 
)
sacred pier
who would be the hero though ? Lets be honest about this. The Robot Twins, one being a tab bit more genocidal then the other, their half fox mother who encourages their bad behavoiur, or the British Mutant Turtle Mad Scientist ? no mater how you look at it. It would be a Villain Stream. You could probably make an argument of Evil being the least evil of all of them. but still It would need to be other Vtubers to play the hero.
could be a Magical Girl Vtuber team up against the Wicked Vee Dall and his Robot army. maybe even a powerrangers would be a neat theme. Toma would fit Pink/Red depending if we go with Magical Girl or Power Ranger.
autumn ferry
perhaps half the joke would be the hero not being so heroic