Yeah well, you have a point, an absolutely minimal PID 1 will probably have fewer bugs than systemd.
Anyway, I think the risk is tolerable. I have never seen systemd crash on the systems I've been using. Also systemd doesn't just abort on SIGSEGV, it serializes its state and then execs itself anew. The code to do that is used in other places too (i. e. configuration reloading and reboot-less upgrades), so it's not some obscure code path that is never tested.
You'd have to be very unlucky to hit a bug that makes systemd crash and corrupts its internal state enough for the recovery mechanism to fail.