What's the point? How is typing foo::bar better than typing foo_bar?
It seems like you want the language to be more complicated for no benefit. Why not use C++ at that point?
> What's the point? How is typing foo::bar better than typing foo_bar?
You're missing the whole point of namespaces. The goal is not to replace foo_bar with foo::bar. The whole point is that within a scope you can type bar instead of foo::bar, or bar instead of foo::baz::qux::bar, because you might have multiple identifiers that might share a name albeit they are expected to be distinct symbols.
Namespaces don't need to be mangled at all if they are interpreted as symbol prefixes.
I'd prefer that, say, namespace foo::bar resolved into foo_bar for all symbols (even that meant risking namespace naming collisions) to not having any support for namespaces in C.
In fact, this approach is already used to implement pseudo-namespaces, so that wouldn't be much of a stretch.