In principle the idea is not bad. There are the so PVP and the RP servers but these are rule sets (easier to deal with) and not mechanics changes.
IMO from the devs point of view this would actually be hard to implement (granted I am not a programmer and can only speculate how hard things like this are) considering that all patches load up first and then you choose the server. ON the other hand the test server is working differently... so maybe it's possible to do so.
Has to the definition you make I am not sure if I agree. I am not a hard core player and I like the difficulty has is. Plus even the casual player would like the mounts and boats.
Maybe it is important to define Casual, Core and Hard-Core. I consider myself a casual player. I'm not always on and only play an hour or two a day (at the moment no time for more). But I like the difficulty and don't mind to progress slowly. Actually I wonder if the point are these categories. I think that some ppl just want to do it faster and that's it. Or just care for raiding (which I don't consider to be a hard core gamer just because one likes to raid). So in the end what are we really talking about?
Sorry I have to go now for a meeting....

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Arkrnum : Raki Sorcerer / Minerologist
Sideroth : Kurashasa Necromancer
Siul : Vulmane Ranger
Shadows of the Dragon Guild ~ Gelenia Server
www.shadowsofthedragon.com