I Will look into this and see what can be done.
I see there is API to detect the owner of the monument so I could work off that with XPerience and possibly add in 2 new options.
Only allow monument owner to gain XP and Allow monument owner team members however there will need to be an option added to Monument Owner plugin that also allows team members to access crates and such so that when a player tries to access it they get added to the data correctly.
The way XPerience works, when a player loots a crate or container it adds the container ID to cache and a list of all players who access it so that way the next time they try to loot it their ID is already listed with that crate so no more XP is awarded. I am guessing the Monument Owner plugin prevents the hooks from adding the crate and player to the data although it's odd they still receive XP for it.