- Dungeons as we know them today, for leveling and initial max-level gear. Awards blue gear as is done today.
- Heroic dungeons, scaled up in difficulty from today, awards LFR level epics, levelrange 88-90 (awards nice xp for the people able to do them and/or provides a nice way for guildies to help eachother level the last bit). The alternative for people who consider themselves good players and who doesn't want to deal with the laidback LFRs. New Heroic dungeons should be released in line with new raids. Need not have normal mode counterparts (but could). Queuing to these should be like queuing for Heroic scenario/Flex is today.
- Looking for Raid, as we know them today, levelrange 90.
- Flex, as we know them today.
- Normal mode raids, increase the difficulty slightly from today. But decrease the itemlevel differences between normal mode raids a bit so slightly older content isnt invalidated as fast. Should be the endgame aim for casuals.
- Heroic raids, separate from normal mode raids (not the same raids). This should be the really difficult ones. Increase the difficulty some from todays heroics. Doesnt have to be as many or as large as the normal modes. Remove them from public test realms so everyone starts out the same. Should be the endgame aim for hardcores. Substitute for "bonus" bosses on todays heroic mode.
Should be plenty of content for everyone like this, with alternative gearing paths:
Casuals: dungeons -> LFR -> heroic dungeons -> Flex -> (Maybe) Normal
Hardcores: dungeons -> heroic dungeons -> Flex -> Normal Raids -> Heroic Raids
Both get to see almost the same content, with the exception of the bonus bosses. And even they could still be seen, if not conquered if they werent put in a linear design (have to kill boss A before you can go to boss B).
And, hey, let's throw a wild idea out there: Normal scenarios could be on par with normal dungeons, but throw in some heroic scenarios that range in difficulty from heroic dungeons to heroic raids(!), with appropriate loot.
And last but not least, but a disclaimer on the heroic dungeons/scenarios so people understand that it's not for facerolling with green gear anymore
Of course, this is just a rough foundation; there's plenty of kinks and stuff I'd iron out afterwards; especially the itemlevel differences between patches, which is just horribly large in my opinion.