This: C or C++.
Part of what I do is writing books on programming.
Ok you have pretty much have lost the argument by trying to use your credentials to improve the argument.
Its NOT how. How is the easy part. Thats just basic boolean logic.
Actually not, your first post is impossible to implement. By definition you can not award a proxy kill to someone you already hit with a bullet.
AH are going to be writing code with or without this feature going in. In this context the hard part is getting to yes. Is it really better to get credit, a kill, for an object you did not influence in any way. Some would say yes!
This is the easy part, it is simply subjective opinion.
The other side of the coin is BAM! You hit a tree by mistake (or one of another myriad ways) and just gave a free kill to someone for doing nothing.
I believe you stated the same side of the coin again not the opposite. Both ways you assume the person getting credit for the kill did nothing.
I'm not bent outta shape on this wish. I dont think it is unreasonable either.
Cheers 
You seem to completely miss the case of being chased, and hence die in a collision do to that being chased.
You seem to ignore how your idea promotes miss use by simply colliding to prevent awarding a kill.
P.S.
The answer is no to your wish.
HiTech