I once designed a rogue in 3.5 edition that was high intelligence and had all skill points in non-combat skills. No trapping, no locks, no hiding or moving silently. It was all the skills you would need to be a diplomat in a campaign that took place entirely in a city with little combat.
Obviously such a charcter doesn't work well in combat MMO's, but one thing I would like to see is someone that specializes in every non-combat option the game has to offer. It would most likely be a rogue (but could be any class really) and it would have the ability to pass all non-combat skill checks. For example, I've never played a character that was actually able to pass the wilderness lore check in mask of deception to poison the meat (I played the classes that could do this before the quest was released).
A single class that can pass every wilderness lore, religious lore, arcane lore, diplomacy, bluff, intimidate, UMD, etc. check that the game has to offer would be nice to have. It would still need combat skills because there are not many opportunities to do anything other than fight, but it would be nice to have an option for one character that can take all the non-combat options when they exist. I'd still have this rogue able to trap, open locks, and hide in shadows, but this archetype tree would offer lots of place to put AP points that boost these features. Thus, the rogue would be less good at combat than most rogues, but still enough to get by and able to enjoy the dialogue options we usually ignore every life. Just make sure they don't hurt the combat abilities so much that it is just a flavor build, or no one will play it.