Idea to optimize images

[GurliGebis]

ISSUE

Currently, every image (cm, cd, rep etc.) are created from scratch, resulting in a huge download when downloading the images.
An idea might be to use a multistage image, and then have a stage where a sitecore instance is copied into the resulting image.
Then after that, App_Config and Web.config is overwritten by the version that matches the correct Sitecore role.

If you do it this way, there will be a layer containing all the sitecore files that will only be downloaded once, and then a separate small layer for each of the roles, improving download speed, storage requirements and load on the container registry.

My idea would be like this:

1: First copy files for the CM role into the destination C:\inetpub\wwwroot in the Dockerfile
2: Then, in a separate command in the Dockerfile for all of the roles, copy the App_Config and Web.config for that role into the folder, overwriting the files from the CM instance.

By doing it this way, everything should be smaller.
From what I can see when downloading the images, there is no optimization for this (please correct me if I'm wrong, since I cannot find the sitecore assets image anywhere to inspect).