Yeah, I dun really know how the kick gravity kill counter works internally. It doesn't seem so trivial. Could be done with a player slot that keeps track who kicked the respective player last. But then again a lot can happen between a kick and a fatal landing. Is the slot wiped when the victim player moves/jumps a bit on his own? By time? When he is hit by other people? Anyone tested that?
Maybe I'm just not seeing the easy solution.
I think the easiest would be exactly what you said.
Whoever nudged/kicked a person last gets the kill in case of gravity death and this slot would be wiped by time.
3-5 seconds should be good. In case of a high wall it should not take longer than 5 seconds to get nudged onto an edge, wiggle around attempting to run back on the wall realising it is too late and falling to your death.
A nudge towards an edge and the victim somehow jumping down on their own, or after taking a hit or whatever, should not be relevant during those 5 seconds, since the nudge was the inital bop that made the victim get too close to the edge.
Might wind you up if you actually hit someone last and he falls and dies and someone else gets the kill, but at the moment you would not get the kill either, unless your hit made them tumble back into their death.
But the additional satisfaction when nudging someone off an edge AND getting a kill would make more than up for it in return =)