I'm not Pat, but I would also very much welcome R128gain implementation in MusicBee.
Be aware there have been some heavy discussions about how to tag the results, using existing ReplayGain tagging fields or not.
You will also have to make some choices and maybe some adjustments about that...
I haven't found an ebu r128 tool that didn't also change other existing tags in mp3's. (or even worse, re-encoding them)
So it would be really great if you could find a way to make use of the superior ebu r128 algorithm from within MusicBee where it just works, without messing up tags or re-encode MP3's.
Default settings as presented in the latest R128Gain version in my opinion would be fine, maybe with a selectable option to lift output level with 5db to get closer to ReplayGain levels.
(even if it is just to prevent a torrent of questions like: "why is my music playing at such a low level after i used the volume analysis function?")
I hope you'll find a way!