Extending the PvE, PvP, RP ruleset?

There is no denying the tension between casual and more hardcore gamers. It's an ongoing struggle, and I think its fair to say that hardcore gamers are those that ultimately get neglected. So why not solve this with more diversified realm rulesets? Just as the PvE and PvP ruleset allow people to participate or ignore player-vs-player combat, why not also let players join like-minded with rulesets for difficulty and cross-realm functionality? Realms could be designated as Pooled or Isolated and Grind or Standard. I know grind is a dreaded word but would serve more as a warning.

A recipe for realm peace or would these rulesets result in too much segregation?