I don't see much of a point in this, ok you can maybe save 25 mins, but how often do you install windows ? Besides, when reinstalling Windows most of the time is spent on installing drivers, applications and customizing (themes, changing settings etc..). 25 mins makes no significant impact on the whole process.
And you never know what you are missing, do you know exactly what setup.exe is doing for that extra 25 mins ? It may not be just copying files back and forth. I don't want to mess with an installation to save a mere 25 mins on something I do once or twice a year and risk facing grater consequences down the line.
This is just my opinion..