I feel there should be, when you allow someone to your lot, a way of setting a tier of how "allowed" they are. Depending on how easy or hard this should be to program (I don't know - haven't seen the way IDP is programmed), maybe you could make it so you can assign certain "permissions" to people on your lots.
Some examples of the permissions could be:
Toggle levers and/or doors and/or waypoints - Ability to deny or allow people to toggle levers,doors and waypoints, preferably separate permissions to make it more customizable?
Destroying blocks - Ability to destroy blocks, separate from being able to place blocks - maybe not a good idea, but still
Placing blocks - Ability to place blocks, separate from being able to destroy blocks
Administration powers - Like a "co-owner" feature, will give them owner powers except they can't modify the owner's permissions nor other "administrators" of the lot. Could be abused, so only to be used when the owner absolutely trusts the proposed "administrator" of their lot
I realise you can do the lot-wide modifications with groups, so probably not needed - just a thought.