Busybox is frankly a horrible user experience, and will never be a good one. Its niche is to be as small as possible, as a single static executable, while providing most tools you need to get the job done in an embedded system. Bells and whistles like a shell that's nice to use, or a vi implementation with working undo/redo, or extensive built-in documentation in the form of --help output, are non-features which would make busybox worse for its primary use case.

It doesn't have to provide any user experience. It can work like dash/bash already do: there can be a minimal/fast/safe/POSIX shell to run your system, and an other shell facing users.