OpenRC is indeed a shitty service manager. I really can't see the hype behind it. The fact it's used in gentoo doesn't make it a good system, more people should understand this. Runit on the other hand implements way more good practices, even though some people reported issues with it when dealing with systems with a lot of services (especially with service restarting/failure detection).

For the core utils, you neither busybox nor toybox are POSIX compliant, making them poor alternatives to coreutils which is POSIX-compliant (but adds a shiton of useless/bloated features on top of their utils, making them unreliable and bug-prone).
There is the suckless base which is fairly good and POSIX-compliant. They also provide a way to build a sbase-box binary if that's what you really want.

Regarding the package manager, packlim is indeed fairly interresting, but I don't know how one would integrate it in another project than rlsd2.
I like the way it handle packages though. This result in a really simple format for packages, and it even has package signing.
I don't understand much why the author added a TCL interface though.
There is also no documentation for the build system, which seems interresting, but makes use of many different technologies, resulting in a big mess to me (makefile, shell scripts, TCL, json, ...).