Re: Use of Japanese terminology...
It is very important, like you said we do practice a Japanese Martial Art and if we were in Japan we wouldn't be speaking English for example.
Also if you go abroad to train where you are not accustomed to their language, then the terms that "should" be used would more than likely get you through a session. If you can understand that?
We should try and keep the true spirit of Aikido alive and that I think means the language usage has to be Japanese.