Given the relatively stable state of most of Yamatai's holdings, a third XF plot ship of this type could probably rescue those stranded by pirate attack or mishap in the Halna area.
Another, similar idea - with the developments IC with the Mishhu, a joint Nepleslain/Yamataian plotship for securing law and order and recovering refugees on the on the new DIoN holdings might be exciting- a joint plotship because it's ostensibly a Nepleslian-controlled area, but DIoN likely doesn't have the resources and manpower to bring order to that many planets quickly. Many of the captured planets were probably originally Yamataian, and some of them probably still have Yamataian survivors on them that might need to be rescued and maybe relocated.