Today I will share with you an idea that may work. I'm sure you guys came up with this but didn't want to.
New users will have to wait 1 week to upvote and have atleast 25 posts. Current users will need 25 posts and a total of X hours online from website (Being online won't be counted if your afk, im sure this is possible)
New users cannot Negative vote until 1 month of being registered (to stop neg rep revenge smurfs(people creating accs and rep fucking the victim))
Maybe try and further comprehensively upgrade the idea to something optimal and agreeable?