[neolog]

I agree there are a number of interesting packages in this space (Metatheory is another).

What I'd like to see more of is things like arrows, higher-kinded data types, etc, that work better with support from the language's type system, and things like parametrized modules and contracts, that just need someone with the right background to show Julia how to do it well.

[BadInformatics]

I'd like to see those as well, with the caveat that I've yet to see a language implement some of them performantly (e.g. arguments against higher-kinded types in Rust).