Exhibit A: Player in one of my leagues has 89 Baserunning and 100 Speed. His lifetime major league SB stats are 487 and 15. He's 97% lifetime, 98% in this, his age-30 season.
He's had seasons of 120, 116 and 107 SBs. He's already ridiculous.
Because SBs are set by TEAM, his teammates are a few guys going 3 for 10, 5 for 12. That kind of thing. His team success rate is around 75%, which is still pretty high. I would guess his team setting is Aggressive, because there are a few other runners on the team, and the team is among the league SB leaders.
If you customized the settings by player, you could run this guy on Very Aggressive. He'd steal 160. You could make his slow teammates never run at all. His team success rate would end up around 95%.
I'd guess that to reprogram the base running settings to make them individual, you'd have to recalibrate the baserunning ratings completely.