Being able to turn into other humaniods.
Mind control.
These are the core content. I looked to Handy CO book, but couldn't find much. Is there something I'm overlooking?
Looking to build the best doppleganger I can, I want a mind**** bard pretty much. I thought about going the MH doppleganger class but the LA is a bit to high for my liking. All books are availible to me. I just can't find anything that fits into what I want.
Being able to turn into other humaniods.
Mind control.
These are the core content. I looked to Handy CO book, but couldn't find much. Is there something I'm overlooking?
What level are you starting with?
The easiest way to do this is to avoid the doppelganger itself and instead aim for your control idea using the Changeling (Eberron Campaign Setting / Races of Eberron, and MM3 I think).
The changeling gets the transformation abilities, but it's purely cosmetic without some feat support - still, that "purely cosmetic" still works wonders for mind games. It realistically just means you don't get all the ability scores and special powers of your new forms. Most importantly, it's also LA+0.
For mind-control, the best class is actually telepath (big surprise), but it doesn't get the same level of support that the others get. A bard / Mindbender 1 / Chamelon X would probably be a stronger overall character, but it will take a teensy bit longer to get access to Dominate abilities. (If you follow the Adaptation advice for the mindbender and/or Chameleon, you can use telepath -> Mindbender -> Chameleon and end up just about as good, although you will have some problems augmenting Psionic Dominate to the higher levels.)
Bard is a pretty solid starting point to get into, especially if you work in, as TS suggested, Chameleon. You'd have a nasty array of skills and abilities to mess around with.
The telepath is good, but unfortunately so many DMs frown upon psionics
. You can also look at the soul manifester (assuming the online psionic material is allowed) since you can also use the charming veil soulmeld to boost charm and compulsion DCs in addition to using your psionic investment ability to boost individual powers and you've got workhorse powers like psionic dominate that live or die by their save DC. You would, however, need to use one feat on Shape Soulmeld to cover both the shedu crown and charming veil, since they appear on different class lists.
The psibond agent (from Complete Scoundrel) offers a slight different tack, restricting itself to just one or two affected targets, but being usable at will while including a solid skill selection and some sneak attack. It's more of a secret agent mind-controller as opposed to a powerful mage-type mind-controller, which gives it a feel more like a typical doppelganger.