Apparently I wasn't careful enough to avoid this sort of response with the statements of
most character concepts and the request for people to cut me some slack about this. Oh well.
Here goes...
Irda Ranger said:
You mean they'll be able to make them in June, or "eventually"?.....
....There's simply no way to "re-theme" any of the 4E base classes into a Psionicist (they've stripped out most of the Ench/Charm spells, remember?). No illusionists. No necromancers. No swordmages in June.

How would you make Haplo from the Death Gate Cycle? What about an Akashic from Arcana Evolved?
So in a previous post I have addressed the psionicist, necromancer, illusionist, and shapechangers. They will probably come out June 09 in the PHB2. In the mean time play a different class or try to shoehorn some other class to fit. I was trying to be helpful to people who were actually confused with how to convert characters, not folks who already know how to do this.
That being said, I would probably play a wizard or warlock and see if I could get the ritual rules to fit my ideas of enchantments or necromancy. Don't know about the others. I have never seen an Akashic or Haplo, so I can't help you there. Without knowing anything about it I would suggest that you should make sure that these roles can't be done with out of combat rules before you write them off. As I said though, I know nothing of these things.
Irda Ranger said:
Plus, there are many systems of magic out there that just don't mesh with D&D 4E. The novels of Jack Vance spring to mind.
I disagree with this. Just because you are not forced to play a vancian caster through mechanics doesn't mean you can't play one through fluff.
Irda Ranger said:
But there's a broader problem: not all fantasy characters stick to a clear combat Role (Gandalf); others are just too powerful (Rand al'Thor). You simply can't make these "too good for PCs" characters. I think the combat role system will work out fine, but it is restrictive (in a good way, for a game).
I mostly agree here. I stated that the concept had to be reasonable, and what I meant was that the concept could not be what another poster on these boards called a Mary Sue. Toning these characters down a little would make them workable though.
So to the rest of your post I will respond with this.
<----Check out my post count. I'm a noob.
That being said, I think that there are many posts on these boards that may not be helpful to you. Please ignore them. I still think that if you were a little more open to this you could get something out of it. The bard thing is a start. Just because you have a fluff reason to justify your style of bard doesn't mean that it isn't possible to create it without an official bard class. I have been "mesmerized and enchanted" in the real world by real, non-magical musicians. I bet if I saw their resume it would not include the bard class at the top. Most of this is out-of-combat stuff anyway, so maybe rituals would work?
The berserker works the same way. I saw a fight once where a guy got so mad that he drooled! And broke stuff! And even hit his friend! And he was a wealthy New Englander.
You are right though. If you don't want it to work out then it won't. There is no way that anyone can help you. These were just some suggestions for how it could work out. There still are a lot of questions left unanswered, I could be completely be proved wrong in June. At that point I will just houserule everything back to the way that I thought it would work, and be happy for the changes that I feel were good.
Well I am about as far from New-agey as it gets, but when it comes to RPGs, we are all just pretending anyway. I think that Hong says it best when he says that this would all go away if we just didn't think too hard about fantasy. As will all my previous posts, take this as you will, leave it for some one else, whatever, but many people have gotten something from this, and some just won't.
EDIT: Thanks Katahn, I beleive that you have succinctly summed up the options for conversion. Probably for those players who want to create their Baby, the one they have been playng for ~30 years, there will be no satisfying option. If they didn't want to change characters is ~30 years, changing the character sheet will probably be traumatic as well.