to actually address in the initial post:

Many developers from Blizzard to SE have explained why "Pre-Patch/Expansion X" Servers or after-the-fact "Hardcore" Servers are a complete no go.

IN the Case of the former it is a two fold reason, First, the population of players that would want to play on these servers is too small that maintaining different iteriations of the code is not cost effective. Second, as Blizzard pointed out, when a new iteration of the code is implemented onto the live servers, the old version is discarded...there is no rolling back to "Pre-Whatever" because the base code for "Pre-Whatever" doesn't exist and may need to be completely rewritten in order to reimplement it, which brings us back to the first reason of population being to low to justify the cost.

As to "Hardcore" servers, when none had existed before, well again it's a case of Population would be too low to justify the cost of coding and maintaining them, is the primary reason most developers say "No".