> I think the disadvantages can be solved by non-pure functional languages, and that there is a lot to gain for new programming languages in this area.

We don't necessarily need new languages for this. There are already pragmatic languages out there, for example, OCaml [1] (and if the syntax is off-putting there's ReasonML [2] from Facebook). I'm sure there are other examples too.

[1] http://ocaml.org

[2] http://facebook.github.io/reason/