Wow, just wow.
So in writing this article, I never imagined that the biggest argument against my assertions would come from a guy angry about not being able to use a race that mostly needed a lot of splat/houseruling in 3.x and a guy that wants to make a relatively useless character, but feels that 4e has not laid out design space for useless characters.
My answer to the useless character is that it sounds like this character concept is built around the areas of play outside of combat. This is relatively easy, because it sounds at this point like most any out-of-combat role can be created with any class. The in combat stuff is then easy to role play. I would bet money on the fact that no matter what the game, you can play virtually any character as useless in combat. Even if a whole bunch of shiney fancy combat powers show up on your character sheet, you are in no way constrained to use them. Just ignore them and play your character as useless. This may be the easiest character to convert to 4e. If I were to begin character creation with the goal of creating a character useless in combat, I would pick wizard as my class, mostly because they have the lowest HP, no armor, and few weapon proficiencies. Then I would never cast any combat spells. Problem solved. Useless character.
For the problem of not being able to create pixie characters, I would say you were way outside standard 3.x design space to begin with, so your comfort with being outside of the norm should free you from whatever constraints that you feel that 4e has enforced upon you. Hack up an eladrin and create a pixie from that. You already get a fey to start, and the eladrin has supernatural movement capabilities as well, so a little creative modification is all you need. That is realtively easy, and there is the possibility that the MM will have rules for creating pixie characters anyway. Any which way, 4e appears that it will have the transparency to allow this kind of hacking of the rules to suit, without the threat of unintended unballancing of the party.
For the lack of a bard, I would say play a warlord/wizard. No need for a bard class. For a druid, go Fey Pact warlock/cleric or Fey Pact warlock/warlord. For the Barbarian go any number of things from ranger/fighter to straight fighter. Most of what makes a character a barbarian is background and 3.x mechanics that are easily fluffable in 4e by saying that "My Barbarian (actually a fighter) goes BERSERK!!!" The only problem that any player might face with these conversions is an attachment to specific 3.x game mechanics. The character has never had any connection to these mechanics. To the character, these mechanics are just metaphysical constructs that have no practical meaning. Any character can be translated pretty easily. Many game mechanics will be left behind.