

This is ignoring the geopolitical reasons that English became the worldwide lingua franca and is reverse-engineering the reason from a single example.
Chinese was the lingua franca of the sinosphere for centuries.
Imagine if it was China who had the power and expanse of the British Empire, it’s not like a non-tonal non-logographic language would suddenly appear and become a lingua franca for no reason other than it being easier to learn. That’s just not how lingua francas come to be.
Though you could argue that if Chinese became the worldwide lingua franca, the efforts to romanize/alphabetize it would have more force and the language itself might change. Vietnam, Korea, and Japan all had their own movements to move away from Chinese characters (with VERY different motivations/outcomes in each country).
But I really disagree with your premise that difficulty in learning is what decides a lingua franca.






I’ve talked about this before but a logographic lingua franca has a lot of potential to create text that is legible in any language. 1000 years ago, the Chinese writing system was used all across East Asia and you didn’t even have to know the spoken Chinese language to read it, even though the sentence order could be totally different.
There are definitely a lot of problems with this idea but I think the positives outweigh the negatives. (And of course, everybody should also keep their own language’s writing system. You could write in a logographic lingua franca if you were expecting to communicate with people who don’t speak your language.)