Why? Powershell innovated a lot over bash - try and kill all processes started in the last hour with bash, then do the same with posh (hint: a regex is a terrible, terrible way to deal with time). MS could do something good with package management.

Try writing a Powershell cmdlet in a language not designed by Microsoft.

Any language that has a .net VM implementation can do it, including Python and Ruby, which weren't designed by Microsoft.

IronRuby is a dead project and IronPython was heavily written by Microsoft.