Basically, libra (which would be based only on usd, eur, pounds and yen) would decimate local currencies. If used broadly, why would anyone use local? Binance research suggests something similar, but in a wrong direction.
If you earn USD, why would you want to take (partial) FX risk on yen, pounds and euros?
True, that goes without saying re the dollar.
What I am talking about is the following: if, theoretically, libra becomes popular for exchange in countries outside of the big four currencies represented in the 'basket', I can foresee citizens of those countries abandoning their local currencies.
Why would they still transact in rupee/lira/peso/rand when essentially a basket of stronger currencies is available?
USD is the global reserve currency. Making it a basket of currencies is very international but unnecessarily complicated things, in a way that a Venezuelan with a grade 3 education will struggle to understand.
Facebook dun goofed. It should be a USD stable coin only.