It is probably too late now to do something meaningful. Like it or not, ISIS and other Islamists groups are now reasonable well trained, and what is more important they have enough knowledge and skill to train new recruits . Those defectors from French FL and others were significant in the beginning when Jihadi organizations didn't have many members with formal military training (especially Western professional training ) . Now, after years of fighting , they have become self-sustained war machine difficult to stop .