> talent shortages are not acceptable - and I don't buy the argument that "smart people are attracted to non mainstream languages which is how we find smart people", it is simply not true that "most smart people program with Scala/Haskell/Elixir/whatever" - there's smart and smarter working on the mainstream languages.
Smart people can be trained in any language and become effective in a reasonably short period of time. I remember one company I worked at, we hired a couple of fresh grads who'd only worked with Java at school based on how promising they seemed; they were contributing meaningfully to our C++ code base within months. If you work in Lisp or Haskell or Smalltalk or maybe even Ruby, chances are pretty good you've an interesting enough code base to attract and retain this kind of programmer. Smart people paired with the right language can be effective in far smaller numbers as well.
The major drawback, however, is that programmers who are this intelligent and this interested in the work itself (rather than the money or career advancement opportunities) are likely to be prickly individualists who have cultivated within themselves Larry Wall's three programmer virtues: Laziness, Impatience, and Hubris. So either you know how to support the needs of such a programmer, or you want to hire from a slightly less intelligent and insightful, though still capable, segment of the talent pool which means no, you're not going to be targeting those powerful languages off the beaten track. (But you are going to have to do a bit more chucklehead filtering.)
> if you are using a language that the AI knows little about then there's little productivity related benefits coming to your development team.
This is vacuously true because the consequent is always true. The wheels are kind of falling off "Dissociated Press on steroids" as a massive productivity booster over the long haul. I think that by the time you have an AI capable of making decisions and crystallizing intent the way a human programmer can, then you really have to consider whether to give that AI the kind of rights we currently only afford humans.