IMO a company needs to decide this before hiring people. I experienced English as lingua franca in an US company based in Germany with around 25 nationalities

IMO a company needs to decide this before hiring people. I experienced English as lingua franca in an US company based in Germany with around 25 nationalities and there was no problem at all. In fact, it was a pleasure (and a great way to get travel recommendations!). If the language level is acceptable, people will be able to convey their arguments appropriately. A native English speaker may be more fluent, but the argument can stand by itself, if the culture of the company is right. IMO if people cannot understand your argument at all, you do not have enough proficiency to work in that language.