Toggling Private Workshops
My suggestion is to have an option to toggle workshops as private. Meaning those who are not authorised on the land can't use it. This would solve two problems.
The first, which has been discussed in another thread, is that people can put junk in workshops so the owners can't move it anymore. This will cause problems in the future. At the moment our community is pretty good and void of griefers for the most part, but eventually down the road when territory and resource disputes start popping up. I can see this as being used as a situational devastating hit.
Second at the moment people can go into your workshops and use up your fuel to do whatever they need to use it for. That can get annoying especially if people know they are taking up your fuel on purpose.
So having a toggle to prevent this would be an easy fix. You would still have the option of having public workshops which is a direction I see the game is going with. But also add an another layer of protection for players' property.
As an added note: You could also do this the other way around, have workshops normally set as private and have a public toggle.