If you're worried about idling in farms just auto-kick after 1 hour of AFK or w/e.
When I played, if nobody was in the vicinity of the chunks with your farm in it it would unload and of course then the farm would not produce, so people would AFK in their farm to keep the chunks loaded.
[0] https://www.youtube.com/watch?v=dx5Wd28AKxQ (the video is a couple years old so the current implementation might be different, but I think the basic principles are still the same).
Looks pretty easy to build.