Well my first thing is I would want a defacto norm adopted in the same way that bash is basically available everywhere. And of course we would want it to be something that doesn't have the busted dependency story of Python. And I would like for third party programs to have a rich interface be provided through this new shell.

For example, you can interact with docker in Python with a lib, but it would be amazing if the docker binary just exposed an RPC interface and API for script languages so you wouldn't have to parse out things from output or otherwise try to figure things out when writing shell scripts. This is, of course, the PowerShell thing, but PS's aesthetics displease me and many other people.

Computers are, of course, turing complete. You can do whatevery you want, really. But for example I end up using zsh instead of xonsh because I want to use what other people write as well.

Understandable, the challenge is beating the xkcd one more universal standard.