A minimal image like that would be:
- secure, since it would only include the executables strictly necessary for running
- lightweight, allowing it to run on resource-constrained devices like routers powered by OpenWrt
I know it's not an easy task, but I think that most of the problems lie more in the implementation than in the maintenance. Unless there are major changes to Pi-Hole's structure, once it's set up, it requires few changes to keep working over time.
Here's an example of what I'm talking about, a little work of art: a highly optimized Nginx image just a few kilobytes in size.
Of course, Pihole doesn't need to be that extreme; it would be enough to "just" use FROM SCRATCH.
Just a suggestion...