...So it is possible -in my opinion - to integrate both versions in official FET, reasoning not by day, but by interval.
Can open a dialog with the user to define the number of intervals he wants.
Interval1 = first hour of morning - last hour of morning
interval2 = first hour of afternoon - last hour of afternoon
interval3 = first hour of evening - last hour of evening
And can also define between each interval a constraint of break time.
In this way can integrate the time constraints specific to 2 versions customized in official FET.