Applying mods from custom/private registries

Hi, I am interested in using the s6-overlay base layer for my images, specifically the lsiobase/alpine:3.12 layer. I have a few mods that I would like to use but I don’t want to push them into a public docker repository, I have a private repo managed by GitLab and I would like s6 to use mods from this repo.

I tried adding an environment variable like this to the docker-compose.yml but it does not work:
All I am getting is:
dash_1 | [mod-init] Attempting to run Docker Modification Logic
dash_1 | [mod-init] Applying files to container
dash_1 | tar: invalid magic
dash_1 | tar: short read

After looking at the script located in the container nano /docker-mods I found that the the dockerhub repository is hardcoded.

I guess the only way would be to rebuild the base layer, but I also wanted to use other linuxserver images and having 2 layers is a waste of space.
Not like I don’t have this space, I am just very pedantic.

I am looking for opinions, could we add the support for custom/private repositories to the official s6 layer?

The logic has no authentication methodology, and it exists solely to let people share their mods hosted on dockerhub:

Feel free to modify it to suit your needs, but we will likely not be adding that kind of functionality given the core premise.