The question is how would you deal with them?

Personally I'd restrict ALL accounts, so if you have any general area / community chat channels, you CAN'T use them unless you have a full retail copy of the game or have paid a subscription fee / whatever the payment mechanic is. I'd apply the same mentality to whispers / tells.

So anyone using those chat mechanics has paid money. In the terms I'd state outright that peddling gold will instantly BAN you from public channels and whispers. At that stage, you have gold sellers who have paid you money for accounts and can no longer use them to peddle their wares. All good.

Flag / Notify / Report features need to be present for spammers etc. I assume these are taken care of already? Try them out in beta.

General Chat and other big chats only for lvl 10+ so its not just spamming random names and chat macros.

Those report features a pretty much standard for AAA MMOs. I'm optimistic about that.

The thing is if we all hate them then how do they manage to stay in business? It is because some of those "haters" decide to buy gold from them and that is the ONLY reason they can possibly stay in that business.

Isn't pretty much all you said a common practice in MMOs nowadays?
And that doesn't work because gold sellers hack the accounts they use for selling/getting gold

No game has ever been able to stop gold sellers except by allowing players to buy in game items like DDO, Star Trek, LotRO, etc. Other than Zenimax selling ingame items the only other thing that helps is keeping the economy at a reasonable level in the auction house. When you see stacks of copper in WoW going for a 100g each you can understand why new players would turn to buying gold.

Gun 'em down.