Hey all, one of the fish devs here. It's awesome to see all of the comments and happy users.
We are in the process of scoping a major release (fish 3.0) that can include major syntactic changes. If there's an aspect of fish you would like to see changed, now is a great time! Of course we'll read the comments here, and our issues page [1] is where discussion happens.
We're also welcoming new contributors. It's easy to get started writing completions or with the issues labelled "easy-pick". The core code base is reasonably modern C++ too.
If there is anything I would personally like to see it’s the bass plugin rolled into the shell itself to make transitions for bash and some esoteric edge cases easier to handle https://github.com/edc/bass
Maybe adopt a package manager for plugins too? ;)