Well... here I go. I'll try to keep it brief:
- Porfirio Díaz gone: Easy enough, either he dies earlier (by the time when the Revolution started he was really old, and not quite sound of mind) or gets retired by either his advisors or a military coup. The problem is that you still have a crapton of social discontent pitted against whomever gets in charge -whether it is Madero or Bernardo Reyes-, and with that in mind, a lot of reforms will still need to be done at breakneck speed. Expecting a coup by Porfiristas.
- Madero staying in power could work by having Francisco I. Madero displaying some measure of common sense, something he and his cabinet were sorely lacking (Surrendering your sidearm to Victoriano Huerta... What were you thinking?). He should have had a stronger hand in dealing with the Porfiristas, and have Felipe Ángeles deal with the Decena Trágica if it does come down to it, or have Henry Lane Wilson out of this.
It is likely that there will be a lot of brief revolts before Madero can get rid of the conservatives and start getting done with his reforms. Mexico will be more industrialized at the end, and it will butterfly the existence of PRI (or if it exists on this alternate timeline, it will be different) and the presidents post-1930 will be quite different without the experiences of the Revolution.