> Another issue is that I think I've seen some linux systems don't launch the screen locker until resume, instead of locking before suspend; that's not ideal, because the screen locker will take time to launch and lock the screen (more so if it's got a fancy initialization routine and is a large binary/many libraries to load).

This particular issue is fixed in logind, when you ask it to lock the season/suspend/hibernate it first calls the lock screen, wait it to signal it finishes and them it proceed to suspend/hibernate.

Not saying you need systemd to fix this issue, but it is one of the things that systemd allows you to do correctly without reinventing the wheel.