I think I'd rather the CLI be good, thin, and stupid.
(on-topic) I tend this way (after all, I use Lua). Classic Windows CLI is too limited, Powershell is too weird and platform-specific, and the Bourne shell is a bad programming language that happens to make a good CLI (there may well be an orthogonal relationship here) I did have some ideas for a Lua-based shell, but it seems like such a minority pursuit, really. Bash is Good Enough.