maybe in a config you can set up a White or black list of items that can be used in the plan area im thinking one way i can prevent people from just using the plan mode to build whatever they like and never completing it is to make it so things like beds and chest, crafting tables and so on cant be placed in those areas.

(side note) also another idea i had is make it so that only the person making the plan can actually see the buildings (besides OP or people with the right perm) that could also discourage people from leaving then in planing mode

perhaps just make it so that you can place the beds, chests etc, but cannot use them until they are built...

yeah that even would be fine with me because then they cant actually "live" in the house or w/e there making until its done