OoC:
A proposed structure follows. . . .
Superior Embassy [Generic]
A Superior Embassy is an extraordinarily effective centre of ambassadorial activity.
DDC: 17.
Build Cost: 45 GB.
Upkeep: 0.5 GB/turn.
Benefits: A Superior Embassy functions as a standard Embassy, with a +2 bonus to its free Diplomacy actions.
Also, it covers (i.e., reduces to 0 GB) the upkeep of as many as three of its owner domain's standard Embassies.
Furthermore, the free Diplomacy actions taken via any of the owner domain's standard Embassies benefit from the ambassadorial coördination provided by the Superior Embassy and are conducted with a +2 bonus.
Finally, a Superior Embassy provides a +4 bonus to knowledge checks related to the court of any domain, with which its owner domain has open diplomatic relations.
Restrictions: The Superior Embassy only provides full benefits when the owner domain's court is located in the same province as the Superior Embassy. When the owner domain's court operates out of a different province, the Superior Embassy offers no benefits to other Embassies in the owner domain's ambassadorial network; but it does continue to function as a standard Embassy, with a +2 bonus to its free Diplomacy actions, and does continue to provide the aforementioned +4 bonus to knowledge checks.