there is obviously a huge market for english -> japanese and japanese -> english learning. get some holos to stream with whoever does this teaching -- that way the holos are learning and their fans find it much more engaging.

You could also do something like streaming in basic Japanese and then explaining it for a couple minutes afterwards. Say, for example, I'm playing TABS and talking in Japanese about how good cannons are and how I think I'll win this battle -- I could then, after the battle is over, explain why I used said words, what they meant, and what my brain was thinking. This might be tedious if overdone, but you could do it once out of every ten battles; there is no need to explain everything you say.
And of course the opposite works too, streaming in English and explaining it to Japanese watchers.