Do you know the biggest problem with the stage gates, it's reactive.
Assume that you are actually finding out something very prudent for
you to have a course correction, through the stage gate mechanism, by the time you realize you are already late for taking an action.
The solution is "Flow Gate System"
What is Flow Gate?
It follows the same modus operandi of stage gate in terms of dividing the larger projects into major phases. But the checks and balances are not put at the end of each phase but at the beginning.
In an irrigation system, if you look at it, the water from a large reservoir flows in big distribution channels to the check dams, and then to small canals and then to the further small canals that distribute to the agricultural lands. In projects as well, controlling the flow proactively is called the flow gate system.