He can train with whoever he wants, he isn't GSP and I don't see him beating Penn. I see him getting dominated the way GSP dominated Fitch.
The thing with BJ now is the mystique around him is gone. Joe Stevenson was terrified when he fought him. Florian has no reason to fear Penn more than his other opponents in his career. That could make a major difference.
I think after the first round BJ Penn will have given Florian plenty to be afraid of. Penn is still the top lightweight in the world and he is still an awesome striker and world class BJJ praticioner.
I don't think that mystique is gone at LW. Penn got dominated by the best WW in the world, no surprise there. I think the mystique is still there at LW.