Be nice. Or else.
Love the analysis - our CD continuously has talkings with me over v2-final-final-revised-final.psd bad habit.
Only thing is layers seem a little low for the amount of designs you've have. 400K designs and 2.5M layers would be <10 per design. Are you excluding outliers? I'm pretty sure I've got a couple 1K+ layer docs that should skew that a little higher.
The way I handle this problem is that I have a numbered series of revisions (projectpage01.sketch,projectpage02.sketch,projectpage03.sketch,etc.) and a FINAL folder in the same folder. The final revision gets copied in there. Not final anymore? Just copy in the latest revision.
Easy, clean and always the same for each project.
The world ‘final’ is never needed. It is never going to be the final design.
Just use numbering, the largest number will always be the most up-to-date version.