After Paul conveyed Jimmy's plan to Charlie, he asked for Charlie's opinion.
Charlie was actually surprised that Jimmy would bring Nate and his colleagues over so soon after he returned to the States, but he also knew very well what Jimmy had in mind.
After all, Jimmy did not have much authority with Nate around. Even if he had the biggest stick in the form of Julien Rothschild, complications might still arise.
As such, it was far more ideal to just bring Nate to Julien and let Julien persona