Western missionaries created the alphabets of the hill tribes more than a hundred or even two hundred years ago; the missionaries are no longer involved with the language regulation and their influence is not any more than the UK government has influence over US literati due to the use of the English language. The only "influence" we can speak of is the sense of gratitude towards Westerners which is EXTREMELY common for hill tribes and other isolated tribes everywhere under non-white settler forms of colonial rule (Vietnamese Montagnards, Indonesian Eastern islanders and Bataks, India's Northeast tribes), because the Westerners almost always assisted them with avoiding assimilation into the larger nearby ethnic groups, due to colonial divide and rule policies. In the modern age linguistic standardisation is mainly performed by locals and their diaspora using internet mass circulation, and persuading the public to overhaul their alphabet is incredibly difficult once established. The only way to win them over is to take over the colonialists' role as 靠山 and sponsor them in resisting the larger ethnic group, no need for these 19th century tactics.