I agree that renaming symbols would still save a few more bytes, but I still think that with the right file format, symbol renaming and mangling would become an insignificant, unnecessary micro-optimization.
But that should only be tested in practice, so ... :)
This seems backwards. If I have JS source and the identifiers take up 10% of it, then symbol renaming and mangling can shrink my code size by something less than 10%.
If we shrink that other 90%, so that the formerly 10% is now 80%, renaming becomes more attractive.
This doesn't hold if people have a fixed problem with a fixed solution and fixed constraints... but problems and solutions grow.
But that should only be tested in practice, so ... :)