No surprise that so many people voted Japanese here... but I kinda question why?
Its got definite advantages over English, don't get me wrong, but its got equal number of siadvantages, biggest of which being it's perpetually in flux. Does anyone who voted for it realise just how many of the youth within Japan are functionally illiterate? No, really. I'm dead serious. Its got to this insane point where the newspapers are increasing kanji use because modern computers mean its easy to, and the youth are sitting there in uni writing exclusively in kana. Too many homophones? Thats easy, grab a word you learnt from your failed English classes and substitute in an approximation. Theres more flux in modern Japanese than there is in English, and English is spoken in how many countries?
Whilst I'd very much approve of a common language using a SOV grammatical structure (its stream of consciousness so it just makes sense) I think you're barking up trees here. Finally, I really doubt Japan would want that either, the government loves to utilise the language as an intentional cultural barricade: just look at the ways their internet is closed off.
I'm surprised nobody suggested English reworked and written in Korean hangul: saw a thing on TV pushing that the other day (eh?)