>>106564888 (OP)
I would just build upon a chroot from skarnet (lh-build) which is a minimal s6 based system (init, networking etc).
Your distro will be more unique than classic Sysv like system and it will actually make sense to build upon that, because s6 is modern efficient init while not being bloated cancerware like systemd.
If you want declarative configuration you can look at Obarun and use their 66 which is a declarative frontend for s6 init which kinda allows you to write services like for systemd if you want such thing.
You can then make your own package manager or maybe try to adopt pkgsrc from netbsd or use a linux like port utils like in CRUX. For some reason I can't find the source for pkgutils, but I've found some fork that is actually quite interesting:
https://github.com/Vifon/pkgutils. You can try that or fork it. It looks quite simple so you can check it out.
I've used CRUX for years and it's solid simple system. The pkgutils are very easy to use and you have basically full control of how your packages are going to be installed. You don't need to adhere to some standards imposed by the package manager from major distros. If you wanted to use LFS then you can just write the ports when you are at it. You will not only have a nice ports system, but also a reproducible environment which is fast to iterate on. Alternatively you might try nix/guix for the package management as an exotic alternative but it has steep learning curve. There are also pet packages from puppylinux which would be another viable option, you would be able to simply use their packages.
