I think English has two advantages : 1- it is already very widely used 2- more importantly, it is a fairly simple language compared to French , German , Arabic , Mandarin etc. Can't really think of a language simpler than English
I'd still prefer English to be the lingua franca for two reasons: plenty of exposure opportunities because it's everywhere; non-gendered so you don't have to play mind games about whether a book is m, f, or neutral