You do realize Phoenixstorm, that the orignal Phoenix sagas, both regular and dark, were retconned in '86 when Jean was brought back for X-Factor? In the Claremont stories, Jean and Phoenix were always intended to be one in the same. The powers that be at the time, would only agree to resurrect Jean if the writers could find some way to absolve her character of the atrocities committed by Phoenix. Talk about playing it safe! Ta-da, we then have the Phoenix "force", now an "entity" able to act independently of Jean. So in a sense, one could argue that Morrison, Endsong et all brought Jean's character full circle. It's quite poetic actually, returning to Jean what is rightfully hers and finally allowing her to reclaim her true destiny... her birthright! In a sense, Endsong and all that, is really just a retcon of the original retcon, restoring things to the way they were
originally... MEANT TO BE!
Jean is hardly omnipotent, dare I say, even as White Phoenix. As you said, there's always someone stronger and more powerful. Not to mention, her power levels have always fluctuated and spiked, never remaining consistant as Jean Grey
or Phoenix. She has weaknesses also, as a psi, Jean's vulnerable to sonic attacks and I would assume, magical ones. Anyway, personally, I believe Jean's biggest weakness has always been... HERSELF!
As far as teams go, we need not look any further than the Justice League, the Avengers, or the Defenders. With each of those examples, god-like beings rub elbows with "mere mortals" all the time, and both parties have been equally effective on the battlefield at one time or another. The Avengers have had Thor, the Defenders the Silver Surfer, and the League has Superman AND Wonder Woman. Yet, the likes of Batman or Hawkeye have been the last man standing on more than one occasion... especially Bats(...he's so clever)!
Lastly, whose to say Jean even has to be on a team. She could return and just make guest appearances in various titles for a while before deciding to join one. Better yet, Marvel could get their collective heads out of Joey Q.'s ass and finally give Phoenix her much deserved and highly coveted solo book. It doesn't even have to be an ongoing, it could be a 12 issue limited run, just to test the waters, sort of speak. Trust me, the "Jean Grey IS Phoenix" era has only just begun, so ya better get used to it! Seriously people, deal with it, just... DEAL WITH IT!!!