If I'm a manager, and somebody tells me that the development team wont be productive for months, I'd likely ask for some real metric indicating that Haskell solves / eliminates classes of bugs untouched by other statically typed language.
At least some figure indicating that a Haskell app is less prone to bugs, etc.
I'd probably rephrase "not" to "less". Haskell is sufficiently unlike other languages that a lot of knowledge/skills that are usually transferable between languages don't apply to it. That means you need to (re-)learn how to solve those problems in Haskell if you want to use it.
The end result is _usually_ better (e.g. Lenses are in almost all cases an improvement over getters and setters; Functors, Monads and Traversable are an improvement over imperative control flow), but damn it it doesn't take a while to get your head around those concepts.
At least some figure indicating that a Haskell app is less prone to bugs, etc.
Otherwise why not throw Typescript at it?