The skill bonus can than be used in place of your MIND bonus for any interactions with intelligent creatures.
Bluffing past a guard – sub+CHA
Intimidating the barbarian leader with a show of might – phys+CHA
Convincing the elven court that you mean no harm to their forest – com+CHA
Haggling down a merchant – com+CHA
You can still simulate charismatic leaders by having non-magi with a high MIND stat.