While I'm usually in favor of fun, odd, interesting combinations and manipulations, I believe that technically, the Chameleon class is NOT a spellcasting class at all as they do not have Spells as a class feature.
Instead, they have a class feature which temporarily grants the ability to prepare and cast spells. The class feature Aptitude Focus calls this sub-feature "arcane focus", instead. So I think that the RAW is against this.
However, it would certainly make for some interesting interactions. And I must agree with others in that there certainly doesn't seem to be anything inherently wrong with allowing this combo. So, while I think RAW wouldn't allow it technically, I'd also go right ahead and have fun with it were it allowed at a given table.
No, that does not work.
1. What you want to do is rebuilding, which is designed as an exceptional in-game process.
The rules on retraining allow only substitution levels to be retrained. If you want to exchange class levels, this is a rebuild. The rebuild has tough prerequisites that do not allow it to be incorporated into a normal character creation process:
In essence, you are altering reality in order to rewrite your
characters personal history. Therefore, to accomplish a character
rebuild your PC must complete a significant and challenging quest.
(PHB II, p. 196)
The rules forsee a quest for changing 1/5 of all class levels. Your DM would have to approve your character having completed several quests before entering the game. This is clearly not a regular character creation process.
2. Entering this build by rebuilding would not gain Nar Demonbinder class features.
If reallocating class levels disqualifies him for a prestige class in
which he already has one or more levels, he loses the benefit of any
class features or special abilities granted by that prestige class.
(PHB II, p. 196)
The point is that "qualifying" for a prestige class means fulfilling its prerequisites before taking it:
...the first step of advancement is always choosing a class. If a
character does not meet the requirements before that first step, that
character cannot take the first level of the prestige class. (DMG, p.
176)
Essentially that means you have to meet the prerequisites of the prestige class without taking into account the class features of the class itself. You could not buy skill points with a level of prestige class to enter it. And you cannot take a spell level into account that you only get by virtue of the prestige class itself. These prerequisites (that is why they are called prerequisites) have to be met without the prestige class to qualify for the prestige class. If you change your build so you do not longer meet the prerequisites, you do not qualify for the class.
The example given in the PHB II illustrates this:
For example, a 7th level dwarf fighter could not trade a fighter level
for a dwarven defender level, since his remaining fighter levels would
not allow him to meet the +7 base attack bonus requirement for that
prestige class. (PHB II, p.197)
This character would still end up with base attack bonus +7, because Dwarven Defender 1 lets you gain base attack bonus +1, but not without the prestige class itself.
Thus, if you trade away your wizard levels by rebuilding you no longer qualify for Nar Demonbinder.
Best Answer
I’m aware of seven ways to change feats, but only three of them would definitely work for you:
The “floating” bonus feat of a 2nd-level chameleon, which requires 2 levels in chameleon, obviously.
Losing HD after you’ve qualified for and taken levels of the prestige class in question. Lycanthropy and reincarnate/ritual of vitality are the most rules-solid approaches to that.
Pun-Pun
Anyway, listed in the order I thought of them,
Player’s Handbook II retraining rules
You can swap a feat for any other feat you could have chosen at the time you chose the original feat. Does not explicitly require you to maintain requirements (unlike the rules for retraining class features), but the very first sentence describing retraining in general says
(Player’s Handbook II, pg. 192)
This emphasis, from the very outset, on retraining being a way to change one legal character into another legal character, strongly indicates that it is not a method to create a character that could not have been achieved through regular leveling up. That is, since you couldn’t have taken the 1st level of that prestige class without that requirement feat, you cannot use retraining to become a character with one-or-more levels in the prestige class but lacking that feat.
Retraining also explicitly states that the combination has to have been legal at the time you were making the original selection. That is, using a feat to, say, make something a class skill to improve your maximum rank in it to allow you to take a prestige class, and then retraining that feat to another feat now that the skill is a class skill because of the prestige class, is a no-go.
Psychic Reformation from Expanded Psionics Handbook
This is a 4th-level psion/wilder power that allows you to redo various choices you made in previous levels, explicitly including feats. Its text is shorter and less detailed than the Player’s Handbook II retraining section, but it does say this:
(Expanded Psionics Handbook, pg. 127)
This is a bit unclear, but I would take “the standard rules” to include the “legality” notion in Player’s Handbook II—that is, that you can’t use this to wind up with a character that couldn’t have naturally leveled up that way. But you could check with your DM.
Fiendish Codex I’s Embrace and Shun the Dark Chaos
You know this one: embrace the dark chaos lets you replace any feat with an Abyssal heritor feat, and shun the dark chaos allows you to replace an Abyssal heritor feat with any feat. As you indicated in the question, it explicitly prevents you from pulling requirements out from under other feats and prestige classes. Therefore, its primary form of abuse comes from swapping feats you didn’t have any choice in—notoriously, the four Martial Weapon Proficiency feats that an elf starts with—to things you actually want.
The “floating” bonus feat of chameleon 2nd, Races of Destiny
At 2nd level, chameleons get a bonus feat that they can change to any other bonus feat at the start of each day. Even better, for you, we have
(Races of Destiny, pg. 112)
The “normal drawbacks for no longer meeting a [prestige class] requirement” are... none. There are no drawbacks once you’ve taken the 1st level of the class. There are exceptions—Book of Exalted Deeds, Complete Arcane, and Complete Warrior make all the prestige classes from those books lose class features if you lose their requirements—but for most prestige classes there aren’t.
The ancestral guidance of the Player’s Guide to Eberron revenant blade
(Player’s Guide to Eberron, pg. 142)
which is good, but,
(Player’s Guide to Eberron, pg. 142)
So that’s no good.
Gaining and losing HD
The idea here is that you gain some HD, use the feats (or other stats) of those HD to qualify for something, and then lose those HD (including the things they gave, e.g. feats) but keep the prestige class levels you gained while you had the HD.
You’ll often see level drain mentioned for this. But abusing level drain etc. doesn’t work, in my opinion, because the wording of the level-loss mechanics strongly implies that the level lost is the latest one, and this relies on being able to pick and choose earlier levels to lose out from under your prestige class levels. There is extremely little ground on which to claim that you can do that.
However, with lycanthropy, you explicitly lose the RHD of the base animal, not your latest HD. That means you can use those HD to qualify, and then lose those HD and not the levels in the prestige class. In theory, that base animal could be a battletitan (Monster Manual IV), with 36 HD and thus 12 feats, which is enough to qualify for almost anything.
Another approach that works is to use a race with RHD, and then change your race, e.g. with reincarnate or Savage Species’s ritual of vitality. The belgoi (Dungeon vol. 111) have 4 RHD as a Humanoid race, which makes them pretty easy to use with reincarnate. You can get a lot more than that with another type, but then your DM has to create a reincarnate table for that type—at that point, go with the ritual of vitality, which takes randomness out of the equation. (Realistically, you probably want ritual of vitality anyway.)
Pun-Pun
Pun-Pun can give—or remove—any ability, feat, effect, etc. he likes from himself. There are nearly zero limits on what Pun-Pun can or can’t do, or when he can or can’t do it. The only possible issue he might have is that maybe he is restricted to abilities and such that have actually been published—though, if we’re honest, with the way manipulate form is worded, he honestly probably doesn’t even have that limitation. Which ultimately makes this kind of rules abuse really pointless.