Except in practise, systemd works fantastically and you're all worried about nothing.
Systemd also does much more than that and handles stuff like daemonization and socket creation, so that these things don't need to be re-implemented in every program that requires them.
Bash scripts are overly verbose, repetitive, and awkward in comparison to unit files.
And you can always use sysvinit if you still aren't convinced, just Arch will be optimised for systemd.
...except that those things do still need to be re-implemented in every program that requires them, since most POSIXy programs are portable to more than just systems using systemd.
This being my primary problem with the current upheaval in Linux system organization. Its instigators have mostly made it clear that they consider everything not Linux (or possibly preferably not their favorite flavor thereof) to be obsolete - throwing portability out the window.
Core, deep systems software has subtle bugs, or hidden bugs, or emergent bugs, or any of a whole host of things.
If arch and fedora want to ride this tiger, I guess they can.
Again: init is really, really stable stuff.
Add in hooks to journald, d-bus, and the equivalent of an xinetd replacement/upgrade. Too much change.
And a Really Bad Attitude from the developer. My experience (a few decades of beating around on various tech at various scales) says this doesn't bode well.
Systemd also does much more than that and handles stuff like daemonization and socket creation, so that these things don't need to be re-implemented in every program that requires them.
Bash scripts are overly verbose, repetitive, and awkward in comparison to unit files.
And you can always use sysvinit if you still aren't convinced, just Arch will be optimised for systemd.