The point about how many Brits speak a different language was a reponse to your observation that Brits would need to speak at least one foreign language and that is a red herring. It's actually not relevant because business tends to be conducted in English anyway.
So these European based employees will live in English speaking gettos and be unable to communicate with fellow workers. And their children will presumably be taught in International schools. And their partners spend their time in english speaking coffee mornings.
Mark that doesn't add up.
It might work for short contracts needing a specific skill but not for anything else.
When I do business in France or Spain I use interpreters who have local business knowledge (even in Spain despite my spanish being very good). If I didn't the negotiations would be very one sided. But I also do it out of respect for my clients and I can assure you it goes a long way.
And this raises an interesting concern. If we are going to stay in the EU we need to commit to it and take an active positive role. If we are not willing to do that then I believe we are better out.
As of now bad feeling towards the EU seems to be growing and if that trend continues I will almost certainly vote for exit.