I’ve actually tried doing this (before I made a permanent switch to the sub, hate the 4Kids VA’s now) and I was somewhat effective in removing the Dub VA’s, but the audio sounded awful. On top of the fact that 4Kids cut many lines or scenes entirely, it can be messy. Ultimately, there’s no easy way of doing this. I’d play around with Audacity or Audition and see if you get a better or good result. Good Luck!
I have used Audacity, and I’m still not too good with audio mixing and extraction. What about the second half of the Japanese version?