Why would changing the rotation speed of Venus have any noticeable effect on the outer planets? That sounds more like a limitation of the model than anything else. Especially over such a short time! 20 years is nothing to the orbit of Charon.
Probably, but if a Venus-sized mass showed up in the inner solar system because the Sun just picked it up along the way, it might not be instant death but we’re probably in for a rough time. It doesn’t have to be a black hole that does us in, it could be something much smaller that still strips the Moon away or causes Earth to readjust its own position in a way we, as in life, but also maybe we as in humans or we as in mammals just don’t like very much in a very short amount of time temporally speaking, and we couldn’t do anything about it anymore than we could do anything about a black hole because we’re just not the captains of this ship. We’re just some homegrown stowaways.
But for what it’s worth, it’s also just so incredibly unlikely it’s not a scenario worth thinking about either, and thinking about it too much just invites existential dread.
