How to use mashou

Hello there. I want to write a few words to say good bye to my japanese teachers (female Exchange students who gave a japanese class at my local University) in Japanese.

I also want to propose to meet them in again when I am in Japan.

Can I use また日本であいましょう?

or would be また日本であいましょうか？ better.

Which one is more polite?

You haven't been to Japan nor haven't met them before there, right? Then, I'd say "今度 (next time) は日本であいましょう!" . ! is appropriate, not ? , expressing a strong desire.
However, ”日本でお会いするのを楽しみにしています” looking forward to meeting you in Japan, is more formal.

Thanksk for your answer. No I have not been to Japan yet and have met the teachers for the first time in my hown country.

I mean Home country of course. Sorry for the mistake.

また日本であいましょう!
(Used when you have met in Japan and want to do that "meeting in Japan" thing again)

日本でまたあいましょう!
(Used when you have met somewhere, want to meet again, but want to do that meeting in Japan)

あいましょう？
(a bit strange.)

あいましょう!
(common)

あいましょうか？
(quite a concrete suggestion expecting an answer)

So in your case,
日本でまたあいましょう！
sounds most appropriate.

Hope it helps.