Using pathfinder sorcerer in 3.5

[Volos]

The pathfinder version of sorcerer is much of an improvement over the one 3.5. Would it be balanced to allow the pathfinder version of sorcerer into a 3.5 game to start playing Pathfinder rather than 3.5?
Maybe bring it a little closer to 3.5 by giving it a d4 hit die instead of the d6.

Fixed that for you.

Take a look at the rest of the Pathfinder classes, every single one is an improvement over the 3.5 classes. There are also more ACFs, Racial Feature Subsititutions, and Favored Class Bonuses then you could shake a wand of cure light at. Why not just make the full conversion and give every player a chance to play something that is new (to them) and interesting? Pathfinder Sorcerer is better by far, but the same goes for everything between Bard to Wizard.