Seems to me we're going full-circle on this. There was talk before Trump was even inaugurated that it might make more sense to do a quick ObamaCare repeal and then embark on a longer process of crafting new legislation, as needed, to fix what's still wrong with American health care - which is a lot.
Republicans across the board seemed to prefer doing repeal and replace all at once, but it's getting more dicey by the day to say with confidence they can pass any sort of bill. Remember, even if the Senate bill passes, they still have to go to conference committee to iron out their differences with the House version and then come back and get majorities to support the conference report. You think that's a slam dunk?