Million-dollar question: why do you need people on site? What’s wrong with remote? Unless you have a very small budget for a minimally viable product and want it done in a month (which implies a constant back-and-forth communication in an office space), there’s really no reason to require people be physically present.
Why limit yourself like that?
Elixir being young is misleading. Erlang, the original language of the BEAM VM (in which Elixir also lives and runs its code) has been around for 30 years. Countless telecom equipment and internet backbone tech run Erlang around the world. Elixir itself might be young but the tech behind it is as mature as you can get.
If you are gonna write proposals and will advocate for Elixir (not sure if I understood that part of your post correctly) then you absolutely want to include Erlang and its mature background. If you want to advocate, here’s a link to a huge thread I made not long ago: Please help me persuade a Java CTO that Elixir is the right choice. If you wanna read, you can find a few gems in there, shared by several people.
