By majority vote, there are new rotation rules in place. FATIGUE will police who you pitch next. For most, this should not alter your 1-5 structure, but it will now allow you to go to a 4 man rotation if your ace can handle it (careful about injuries when fatigued!!), and a LOT of flexibility with your 40 man roster.
It also frees up the issue regarding flex scheduling, but it does also create a possible issue of seeing the same pitcher in a single 3 game series if a lot of flex scheduling happens in between.
My suggestion, flex schedule if you have to, but, by experience, it is much more exciting for yourself and the league if you follow the schedule. By all means, use flex if you have scheduling conflicts, or once or twice if bored, but, for the most part, follow the schedule.