This is the approach I take when making drastic changes to computer code, a presentation, or a spreadsheet. When you decide to turn a big piece of work upside down, you can’t simply tear up the whole thing. Instead, you change things carefully, constantly monitoring whether the program keeps functioning, and/or the spreadsheet still produces more or less the same answer. When it does, take the old stuff out bit by bit.
This is the only way to manage mistakes. If you changed 5 things and see that all of a sudden your average price per bottle is way off, you cannot tell which of the five is the culprit.
What if all of a sudden your boss, customer, or user wants an intermediate new version of the model. If you are mid-way in some major rewrite, you cannot produce it quickly.
Or, maybe you discover halfway through that the 2nd change of the 5 you pushed through actually does not make sense. Unwinding everything is hard.