@Steven, you are realizing the same thing I am: sounds simple but a lot more complicated once you get into it. I think with many of us thinking about it and willing to try different solutions we should be able to solve this one.
@Shawn, I have actually already incorporated the majority of your algorithm into the weather service however it isn’t active yet as it doesn’t do any actual adjustments. The code got incorporated here: https://github.com/OpenSprinkler/Weather-Adjustments/blob/master/application.py#L59-129. Again, although the ET is being calculated, it is not being used for anything.
@Wokkeltje no ETA is established yet for 2.1.5 however we did add the feature you mentioned about miniumum time into 2.1.4. The relevant code is available here: https://github.com/OpenSprinkler/OpenSprinklerGen2/commit/6e2d68a655295246aadbd984db34e66524c99e66.