So let me get this straight, you want to make it so that when the player is hit, they get sent flying by the explosion?
Shouldn't be too difficult, I'm sure all you have to do is edit the thing that he fires. Sure he wouldn't have the same speed for firing an explosion ring, but it would probably be the exact same thing. I'd suggest looking up SOC tutorials on the wiki, they'll probably explain it more. I would help more, but I've hardly even started soccing. ^^;
It would definitely be possible with lua though. DEFINITELY. Hell, you could probably do something that makes the entire map collapse with lua.