If you allowed punching and kicking, every person who has ever posted on this website would get totally embarrassed. Yes. Dan Harden included.
Anderson has tapped into something that is beyond the realms of "IP/IT/IS" as discussed on these forums.
As has been previously mentioned, IP/IT/IS, as discussed on these forums, is a separate aspect of martial training than fighting. One does not mean beans regarding the other.
That said, Dan's forte with IP is not aikido, it's MMA. I suspect if they met, it would be an awesome exchange of dialogue, ideas and tactics, and both would learn from the experience. Maybe we'd end up spotting Dan and Steven playing Rock Scissors Paper in Anderson's corner during bouts.
Like I mentioned before, I and others have seen Dan send a trained MMAist literally flying via spiraling within the guy's mount. Granted, that was a friendly demo, but it was clear to the guy who went airborne, and the other MMAists present, that this is not something taught in MMA circles.