I would be surprised if a systemd-based system requires more resources than a sysvinit-based one, but that is of course something one would have to measure for each particular use-case.
How about an init script that creates proc and sys, two devices via mknod and runs one server or a shell such as in any embedded basic example. My favourite init is still OpenBSDs single /etc/rc script that utilises the minimum number of easily followed, edited (though discouraged) and understood inclusions to make administration practical.
There are lots of systemd-based embedded systems cropping up (the embedded world seems more excited about sysntemd than the desktop world). The aim of systemd is to work on anything from embedded, via desktop to servers.
You are actually talking about a fraction of embedded, which is the mobile phone world. In truly embedded cheap instant on devices, udev/mdev (dynamic dev) even can be seen as something that slows down the boot and makes it less reliable than using mknod in a short init script. To reiterate an example some people hope linux will run on a cheap toaster. -- _______________________________________________________________________ 'Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface' (Doug McIlroy) _______________________________________________________________________