I can't imagine the album's Metacritic score if it had a collaboration with J. Lo on it:
And J. Lo is undoubtedly relevant but only as a celebrity because that relevance just doesn't seem to translate into success -- she's had two hit movies this millennium (one of them being animated) and two hits in the past ten years (only one of them being solo and it was a minor hit.)
I honestly think she would overshadow Britney in the video because the collaboration would obviously never be a ballad and let's not even get into live performances.