Ok perhaps your namespaces are the simplest way to 'lift' arc into Nu.
If you implement language A in language B, A is above B in the stack. It's meaningless to call A's code from B, but useful to call B from A. The latter is what I call lifting. But I realize this terminology doesn't work for anything but simple static compilation.
If I wrote an awesome library in Arubic, especially a library that would be difficult to port to Arc, and you wanted to use the library, but didn't want to use Arubic, it would be very useful to write Arc code that used said Arubic library.
As another example, you may want to write a module in Racket that imports a library written in Arc. Even though Arc is implemented in Racket, I don't see how that counts as "meaningless". This example isn't even theoretical, there was somebody on this forum earlier who wanted to do exactly that:
