My grandparents were missionaries in Yunnafu area, up the Salween River. My mother's first languages were Lisu and putonghua. Several of their children were born in Burma. Loing story: most of my mother's friends died in Japanese concentration camps.
I believe culture is bound up in language, its words and phrases worth preserving in living people, not just books.
Unity is a worthy goal, but so, too, is diversity. These languages need saving.