As much as it's a chick flick and ruined life for us common men, Pretty Woman is an all time classic that can only be ruined by producing a sequel.
IMO it is one of the best movies ever made. It wasn't over acted, wasn't cheesy, was heart warming, funny, a little sexy and just an all around great movie.
As we all too often see: a sequel doesn't even come close to the original.
BUT, just thinking outloud, a sequel could go along the lines of:
They are 10 yrs into their marriage and have a girl, the girl is just hitting pubert and the topic comes up about how they met. Mom tells the truth and the girl starts freaking out and tells everyone. Puts strain on the marriage, a breakup insues, Richard Gere has to find Julia Roberts and chastises all the other "rich couples" who looked down on Julia for what she did, and they live happily ever after.
A few of the topics which plague many sps could be brought out and discussed in a mature manner. Things such as:
1) She may have been an escort but she never sucked on the public teat.
2) She was independant and never relied on any one else to support her
3) Also the topic of who her clients were could be brought up to dissuade the stereotype
Etc etc etc.