This may have already been discussed internally at the Blizzard HQ, but here is the sales pitch.
Make 1 PVP server and 1 PVE server of each WoW version that has ever existed with the option to progress leap from one to the next after you hit level cap.
For example, you start a new character on Vanilla Era, then you hit 60, maybe you do some stuff, then you can stay on Era OR you can toggle an option to transfer or copy that character to Classic TBC, then you level there to cap maybe do some stuff there and then you move to Wrath, and so on.
I would personally enjoy this because then you can level though the content as it was originally intended.
This would be potentially its own special kind of Iron Man Challenge; If there were some way to track that in game to prove you did it without any death’s; that would be amazing.
If that’s the goal they failed because “Classic” versions are not really the same, they’re not even on the same engine, or using the same technology; and I think outside the united states it has to be the same software, but different nations are different and have different laws. That is some muddy water tho.
the cost of keeping servers up is basically zero, so not sure why there is any worry about that. Servers these days basically only have costs associated with loads, and lower loads is better; this is why sharding and layers are thing so they don’t need beefcakes hardware. Because of that they could keep non-updated versions of TBC / Wrath online indefinitely.