I did try WIT before, but I couldn't figure out exactly how to use to it properly trim, convert or create ISOs at all.Don't be so sure about that (at least as of around 2-3 years ago, though maybe I should re-test?):
WIT was also mentioned in that thread, though I've never used it for rebuilding ISOs, only for trimming.
It's quite underdocumented at least from what I could find.