Well, I instruct at a group of dojos and the reason I do so is that I am not Japanese. The group had problems with Japanese instructors and wanted someone who understood Japanese culture but who was not Japanese, i.e., did not teach and run a class like the Japanese instructors they had had.
I am not sure that language is an issue. There are quite a number of Japanese terms that have come into English: karate, judo, karaoke, for example, as well as aikido, and I think the reason for this is that there is no English version acceptable to a sufficient number of language users to establish a norm. So far. But I think it is impossible to lay down prescriptive rules for vocabulary use. Speakers use the words that they feel express what they want to say.