Wes, the guy behind AutomaticDuck, recently joined Adobe, so the AD plugins are free now. You could go Media100->FCP->Avid and back, but even exchanging timelines between FCP and Avid is some sort of hassle, at least if you want to carry over the media files. If this is a one time exchange it probably will work, but if you need to go back and forth several times this will be probably a lot of manual re-creation of effects and stuff.