If they do implement an account based voting system there is many other changes that would need to accompany that update to help reduce the amount of abuse right off the bat.
To your point about multiple accounts, there would need to be something that registers which IPs are using which accounts and how many at each IP. This is a scary thought in my opinion especially on a platform that is seemingly attempting to be decentralized. If a centralized authority starts banning people for making multiple accounts then I foresee a lot of anger and frustration in the future. Also, it would take many more man hours to monitor that sort of thing, even with automation. How many accounts would be allowed? Personally I know I had 8 family members in my house growing up. If people have to use multiple IPs to make multiple accounts then at least they would have to pay money to attempt abuse.

I am not disagreeing, these are just thoughts I had in response to your comment. I am not smart enough to know a good solution that would work.