Preface - I haven't played WoW for any length of time since quitting at the end of WotLK. I dabbled in the next few expansions, where it seemed gold was overabundant, not sure if that's what killed the gold farmers/gold bots/sellers, but I didn't seem to see any, or even think I might have a use for them. However, with WoW Classic, I can see a market for them to come back. Did Blizz ever put something in the game to eliminate this after WotLK, or was it the gold abundance that destroyed their market. If not, I see the gold sellers and websites coming back.
Where to get materials and reagents you may ask? Buy for cheap off farmers in bulk or track Auction House lots. Get in touch with most big sellers. Communication is important here, send a whisper or write them a letter. It would be good for both of you to establish business relationships. Constant suppliers and buyers is convenient for both parties to save the time and effort.
All of this is keeping with the spirit of vanilla, which I think is more important than that a specific number be 11 instead of 12. And it would help to "resize the swing" by making the game harder to the more experienced community, and forcing people to re-discover the game rather than simply looking up whatever they want to know on a spreadsheet somewhere.
Before we talk about layering, it's important to talk about the sharding technology used in modern-day World of Warcraft. When a zone in the game becomes overpopulated, players will be seamlessly moved onto a different shard, which is essentially another instance of the same zone. It is important to note that you will still be able to play with your friends, because you are moved to the same shard when you create a party.