So your argument against all sorcerers having Influence as a class skill is that some sorcerers can behave emotionally or irrationally? Because I believe there is an easy solution for that -- if you're playing that sort of sorcerer, don't put points in the skill.
Paladins get Influence as a class skill, as do bards obviously. Rogues don't have to cross-class points into Influence. Clerics don't have to cross-class into influence. You can put as many points into Influence as you might like... If you're playing those classes. With sorcerers, you inexplicably need to make that a cross-class skill.
Well, I morely point that almost everyone can be good with words. Sorcerer do not come with training of the speech. Which a cleric or bard would probably get, since they maybe preach or are all about being quick tongued. Screaming draconian words and raining hellfire on people is not really training your rhetorical tongue.
The sorcerer already get their +4-5 bonus from charisma to show that their charisma will take this far (if you max out your charisma) and that's already a high bonus on low levels. When you start to meet people over level 10 you need some experience in the area since on higher level it might not be Farmer Bob commoner level 1/4. you are supposed to trick with your words but the Inquisitor of Ezra, Harsh Hardson, lvl 15.
There is classes at the university I go to that focuses on speeches, rhetorical talking. A big mouth and fancy smile might take you far with the peasants and the slumdogs, but that is already a factor thanks to your charisma. But to stroll into already influencial and powerful takes more.
The high charisma the class have is already as said! An indictator that the person can be a bit persuasive. But unlike the paladin, bard and some clerics. They do not live off/has it as a part of their life to be preaching, acting or tricking people with words. They got their spells for such things.
