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I believe this thread in a nutshell is one of the examples they gave as to why they have not done a Classic Shard... noone can agree on what the ruleset is supposed to be. There's always a caveat, always a "but..." involved. "The rules should be like this... but... ".
I'll admit from time to time wondering what different rulsets and whatnot would be like. A shard that ONLY allowed the KR client that didn't have to accept different clients to see what the performance would be like, new loot ideas, "anti-magic" areas (like Wind, but in reverse... where you would NOT be allowed in with Magery OVER a certain level), removing Mark from dungeons and blocking existing runes INSIDE dungeons so you could recall out, but not into a dungeon and so on.
It's a fun mental exercise, but it's not really expected that such things will ever happen.
If you're more worried about the ruleset on a given shard than the shard itself, it really starts to take away from that whole "world" motif. It's kind of like an article link I read from another board about a mistake of an "event" in WoW. Much of the article was spent on dissecting the stats of the person involved than on the concept of or the effects on the world.
It's interesting to consider what we would want if we were able to create a specific shard ruleset... but never expect such a thing to actually happen.