I got an nub idea that makes kills are more useful. Add "Skill point", Every player can get a skill point when they got 5k kills. Player with 10k kills can get 2 skills points and player with 100k kills can get 20 skills points etc.
Skill point can add "Str","Dex","Vit","Agi"
"Str"- Does extra 1 damage for Melee and extra 0.5 damage for gun
"Dex"- Walks extra 5% faster
"Vit"-Extra 5 hp in max
"Agi"-5% freeze for gun and melee
Sorry I knew this idea is suck n useless but i wish it helps and sorry if i made some mistakes cuz my English isnt
good Thanks for reading it