Does it add realism? Yes.
Does it add fun? Prove it. I'm 100% convinced that this will lessen the fun of the game. Realms should not require specialist classes, they should rather be outputs for people who like doing things differently. Diplomats are rare enough as it is, making them mandatory for good realm and diplomacy running when player count is eternally declining is absolutely foolish.
I think the idea is to give people more options, and to ensure that realms only keep the treaties that they really need--to prevent the eternal alliances that you see between certain realms. Or at least, limiting the number of alliances that can be easily maintained.
