A PARTIAL WORKAROUND for some situations…
I had this problem. The proxies were made on set and Premiere gave me the audio mismatch error. The shoot was MOS so I didn’t care about sound anyway. The RAW files were recorded without any sound, but DIT made proxies with a stereo sound setting (which was actually blank on the file, but the file metadata shows it). Hence the mismatch error.
I’m on a MAC. I opened the proxies in Quicktime Pro (not version 10, rather old version 7 that allows editing of properties) and in menu chose WINDOW>SHOW MOVIE PROPERTIES (command+J). In the properties window I selected SOUND TRACK and clicked DELETE. I then saved the file and closed it.
Then in Premiere I control-clicked on the RAW file and chose ATTACH PROXIES. When asked, I selected the proxy I had removed the audio from and it attached properly. SUCCESS!
Of course I had 70 proxies and extracting the audio the audio from each one was a drag, but not nearly as much hassel as remaking the proxies from within Premiere.
I’m sure there is a macro that could be written to automate the process, but that was beyond my ability.
I guess if there was sound involved I might have been able to post sync the RAW / proxies with discreet wav files, assuming they were recorded on set. But for this job it wasn’t an issue. I surely would not change the RAW to adapt to anything unless they were backed up.
Good luck!