Finding one good ("best" is subjective, we shouldn't be seeking that)
scripting language to include in base seems like it might have
advantages, [...]
We've already got two or three good scripting languages in base (for
lots of use cases' values of "good"; there are use cases they're a
poor
fit for, but that's true of any language). Do we need more?
Why or why not?
I don't know Lua. But, based on what's been said here, it sounds to
me
like a solution looking for a problem in this context. Even assuming
its touted attributes are real (eg, small libraryable runtime), do we
really have a need for such a thing? I certainly don't recall anyone
wishing out loud that we had, for example, an embeddable programming
language with a small runtime.