I am not convinced this is a good point against hiring someone who lacks depth in your language. It assumes that people already on the team have the same abili

I am not convinced this is a good point against hiring someone who lacks depth in your language. It assumes that people already on the team have the same ability as the potential hire. This does not reflect reality. Different people learn at different rates. I have seen new people pick things up very quickly and surpass those who have been programming in that specific language for years. I am one, myself, with my present job. It is true there is a ramp-up time, but it varies with the person. For some people, different paradigms do not present challenges; they are just different approaches to the same problems. It might be easier for people who dabble around in multiple paradigms to adapt to the new language.