methink you folks are missing the point. forget about kicking in the head and stuffs like that. it's about train the body to do what you want it to do. if there is an opening to the head and my foot is conveniently available, i should be able to "take this foot and put on that side of the face" (billy jack). or if an opening for a shoulder strike or a hips strike or an elbow or a head-butt, i should be able to carry it out. or if there is an opening for iriminage or shihonage or whatever-nage, i should be able to take it without thinking about it. personally, i would go with systema, because those buggers can really teach aikido and karate folks how to move more relax and freely. their methodology would blend in well with aikido randori and freestyle. but then again what do i know, since i only got hit by them a few times which hurt like the ex-wife-of-pain.