Prior to the expansion, I didn't have a lot of opportunities to raid and a similar idea occurred to me. At the time I thought it would be pretty cool if there was a quest for each major raid dungeon that gave the player the chance to explore it without being able to engage in combat with any of the creatures. For instance, at the end of a lengthy quest line throughout Blackrock Mountain and the surrounding zones, you're finally tasked with a reconnaissance mission into the heart of Ragnaros's lair. You'd be able to enter the zone just like normal, but when you arrived inside the Core, you'd be wearing a non-removable Dark Iron dwarf costume. All the creatures would be friendly to you and you could talk to them as you made your way through the dungeon, completing the requirements of your quest. (Check out the quest "Who Are They?" for an example of what I'm talking about.) Perhaps you'd have to deliver a message to one of the bosses or simply visit certain locations in the dungeon, but the quest would have a definite objective and ending. If you chose not to complete the quest, you could keep it in your log and continually explore the zone.
I think this would be an interesting way of introducing the dungeon to non-raiders, especially if it was included as the last step in the quest line that allowed a player to get attuned or keyed to the zone. Of course, experiencing a dungeon is one of the rewards for progressing through its content, but in this sort of scenario, it would be simple to block off parts of the experience for the purposes of the quest. For instance, summoned bosses and those behind locked doors would both be inaccessible to players on this sort of quest, leaving plenty to be experienced later if the player chose to tackle the content in a raid group.
What do you think about this idea? Would you like to see this feature implemented or would you prefer to keep the experience of raid dungeons for those that actually progress through the content?