So, I love the idea of the Synthesist, but even at a casual glance it is obviously terribly broken, so this is my attempt to create something with a similar feel that is not quite so OP. I'd love to get some opinions on it.
I recommend checking out the Masquerade Reveler Barbarian archetype. Even if it turns out to not be something you're looking for, it might give you material to crib from.
Will give your doc a more thorough look-over later =)
The "Epic Meepo Presents Archetypes" thread has a Fighter archetype called the Aspect Armiger. From what I have read in this thread, it is probably a bit weaker than the other archetypes mentioned.
I feel this does not utilize the design space well. An entire class around transforming yourself into a monster has so much potential, why steal abilities from other classes? He shouldn't need weapon training, bravery, and all those perks from the fighter. Those are the fighter's perks. This class's perk should be turning into a monster.
I usually don't criticize style for homebrew content, but I notice you're trying to make your class look professional. However, there's many style flaws. For example, spells shouldn't be capitalized and class features shouldn't be italicized. Look at this style guide I compiled for an RPG Superstar competition. For the context of class descriptions, I have the following guidelines to add:
1) Order class features by level, then alphabetically. If this order causes a class feature to mention another feature further down in the class description, then use something to the effect of "(See below)" to point out that the feature is described later. Weapon and armor proficiencies are always the first class feature listed.
2) Always begin each class feature description with "At Xth level" so the reader instantly knows when they get this feature.
3) Always list things alphabetically. This is mainly for listings like skills and such.
4) Use 3rd person voice. Refer to the class as a single individual of a sex matching the iconic (not applicable for homebrew unless you have an illustration of the class).
5) Always postfix the feature names with the ability type if it's an extraordinary, supernatural, or spell-like ability. You did this, so good job!
6) If the class has a complicated class feature that requires a lot of space, then it's okay to isolate the details of that feature in its own section. A lot of times, these separate sections break the "third person voice" rule. See how Paizo does sorcerer bloodlines and mysteries.