RMS normalization in 'audio gain' window
In addition to the peak volume options in the 'audio gain' window, add an rms radio option, using the lufs (or similar) algorithm from Audition. Often enough, I round trip all audio from a premiere project through Audition just to use the rms normalization to get clips to a good starting volume/gain.
I think loudness normalization at the clip level would be amazing. Using RMS to measure it however would ignore advances in perceptual algorithms that take frequency and time into account.
Jim Simon commented
RMS and LUFS measurement are two VERY different things.
I do think LUFS normalization is the only truly useful option.