I accept the challenge.
It's a little hard to attack on the run as people have said, and actually fairly easy to defend against a running attacker too. I'm a pretty basic-level student of Aikido, but I think that even I could manage a decent neck throw on a running attacker.
Instead I propose that I attack this guy with one of the standard attacks we use for practice in Aikido class, which are clearly intended to harm the partner. This is strongly emphasized, that you must be committed (i.e. give the partner some momentum to work with). If the partner isn't ready or you go too fast for their expertise, pain does indeed ensue (our dojo tends to be nice, so we try to calibrate attacks to the partner). The stuff the black belts do to each other would probably break my arm, or my neck.
So I'm perfectly willing to do a standard punch on this guy, which starts at about 2 m distance and comes in straight to the solar plexus. Or I could do a strike with wooden sword or stick aimed at the body, hands, or knees. No faces. I guarantee pain if it's not deflected, but no serious injury. Where do I sign up?