Sorry for late response, but let´s go.
Idk if it´s possible to apply "sprees" only killing humans, instead bot., as Lazy said, only @daredevil or someone who works with servers can explain how it works with more details. However, i can give my opinion how i think it could work.
I wouldn´t mess with general spree record, like you said, memento has a 736 kills, this is huge. Imagine how much effort he puts in to get it. It´s like KR or PRW, even with bots only, this is a goal for players, get a huge KR and a nice PRW. I´ll speak for myself, if someone one day reset my KR or PRW (stats), i´ll be pissed, becoz over the years, i worked so much to have it.
I dont think if it´s possible to reset map spree record each 3 or 6 months without mess up with general record. This is the first time i saw someone asking / suggesting change on server. If i may suggest something, i would say to reset each spree record on 6 months period, then, we can open the blank space to others.
Oh !MX, so, you are contradicting yourself becoz you said you would be upset if they reset your KR. But, one thing is my personal KR and PRW and they don´t interfere anything for others. Considering you started the topic, we can see someone is a bit upset (and other players can think the same, they just don´t formalize as you did), so, let´s try to work on it.