The timeout issue is often a temporary issue after an upgrade. I need to get into the machine to debug and fix it, but I'm delayed waiting for the timeout.

If they have access to the physical console, they can already permanently interrupt your boot process with an alt-sysreq, ctrl-alt-delete, and likely several other methods (power switch, or pulling the plug.) I'd say being able to gracefully cancel a timeout/retry would be the least of your worries.

If "some rando" has access to the console keyboard while the system is being booted and some service is timing out... You've got a bigger problems than the fact they can cancel the start-up of that service.