It could with a few tweaks, but it lacks features when compared to bash and busybox ash. For example, it doesn't support shell scripting, configuration file initialization, etc. I wouldn't recommended it right now though since it doesn't have most features of a standard shell but if you want to test it out, give it a try.
RustyBox is a c2rust port/rewrite of BusyBox to Rust; though it doesn't look like anyone has contributed fixes to the unsafe parts in awhile.
So, no SysV /etc/init.d because no shell scripting, and no systemd because embedded environment resource constraints? There must be a process to init and respawn processes on events like boot (and reboot, if there's a writeable filesystem)
Yes, you are right, I am trying to create a smaller version of sysvinit compatible with busybox's init. There is still no shell scripting yet, but I do promise to make the shell fully compatible with other shells with shell scripting in a future version.
What happened to RustyBox? c2rust is way easier than doing it manually, then why is it abandoned?
Same question about rustybox. Maybe they're helping with cosmos-de or coreutils or something.
OpenWRT has procd instead of systemd, but it does source a library of shell functions and run [somewhat haphazard] /etc/init.d scripts instead of parsing systemd unit configuration files to eliminate shell scripting errors when spawning processes as root.
There are advantages to systemd unit files instead of scripts. Porting packages between distros is less work with unit files. Systemd respawns processes consistently and with standard retry/backoff functionality. Systemd+journals produces indexable logs with consistent datetimes.