English does serve well as a lingua franca- yes, however Esperanto would serve much better. Ask Chinise people what they think about English, or better ask English teacher teaching English over there... or non English academics who have to write their thesis in a foreign language.
Esperanto is now a real natural language (a bit like a global minority language), spoken around the globe, with some tousands of native speakers .... on Duolingo alone more than 600 000 English speaker learning it. Google a bit or if you like read my article here on Steemit:
https://steemit.com/esparanto/@johano/steem-engine-for-a-global-language
By the way I am a great fan of diversity too.