There is a solution...
- IP address / IP range hashrate cap - this will prevent everybody from creating big farms, just make a cap of share to every IP address and another cap for IP ranges to prevent from Multi-IP addressing.
This will solve the biggest problems:
- it will not consume so much electricity
- it will be more fair play
- it will prevent biggest farmers from affecting the market, 51 percent attack possibility and centralization
An example, make a limit to a single Ipv4 address, another limit to /24 IP address range, another to /20 range etc. The same for IPv6 ranges. E.G. 2 Mhash limit to one Ipv4 address, 6 Mhashes to the whole range, and so done.
There would be people who setup workarounds for this too. Namely big boys who have large up ranges, willing to pay for VPN's etc. then you'll have ip6 to deal with sooner or later as well