> … so that, when you look at an image, or when you use it, browse the code, you can easily see what are changes and what is the base image…

You seem to be asking about something that is in documentation from 1984.

http://stephane.ducasse.free.fr/FreeBooks/TheInteractiveProg...

> i am not suggesting that smalltalk needs to be changed…

Smalltalk has been changed, several times.

"With ENVY/Manager the image becomes a discardable by-product of development, secondary to the repository that stores and coordinates all work."

https://www.google.com/books/edition/Mastering_ENVY_Develope...

"The way ChangeSets are created and managed in Cuis is different from Squeak."

https://github.com/Cuis-Smalltalk/Cuis-Smalltalk-Dev/blob/ma...