I don’t know if this will help, but there is a widget that runs as a service that launches Plex under a user’s login (thus giving Plex access to use GPU hardware drivers). Source is provided, and it has start/stop/show features.
Might be a nice way to do something similar for MCEBuddy (and resolve MCEBuddy-as-a-service while still needing access to the system GPU drivers (i.e. hardware encodes) when installing for “all users” and MCEBuddy should be running when/before anyone has logged into their system. That is typically when something like a power failure occurs in the night or a forced system reboot is required.
The source code is available to see how the magic works.