It is possible..confirmed by two lawyers
I called two lawyers and discussed this issue with them. There should be no problem in switching back to H1b. All you will have to do is to leave the country, get the new H1B approved, get the stamp on your passport from the embassy and return. Offcourse it assumes that your AOS has not be denied on the grounds that makes you otherwise inadmissable. Also it will be easiest to do all these while you got a serious RFE (still have valid parrole) and are sure that AOS will be denied.