Since you insist on using a decently obscure language you available pool talent is going to be considerably smaller then a company looking for C++ or Unity people. You will end up paying more for an F# programmer since they don't have to compete with the droves of new graduates to find a job.
F# is no longer obscure to be fair. I've heard about it almost nearly as often as I've heard "Unity" in the past year.
Functional programming has a lot of pros (it does have a few cons though, mind you).
Currently, the big problem is that there are very few programmers versed with the inner workings.