Another aspect of that: do not do functional programming then. There are statistics for .NET which surely also apply to most languages: 10 million C# devs, 1 million VB.NET devs and 100k F# devs. By requiring functional programming the candidate pool shrunk by a factor of 100.

There is certainly a higher factor of high talent in FP capable programmers but at the same time the risk for bad hires due to lacking people skills or overly dogmatic work style increases.