I do appreciate the effort in trying to understand male to female transgender people who crossdream. I am sure you are right about the feminine cuteness of Japanese popular culture being a hypercorrection to lives imprisoned in masculine hardness. But the connection to “autogynephilia” is not convincing, and I am saying this as one who has worked with male crossdreamers (people who fantasize about becoming their target gender) for more than ten years.
You are clearly aware of the weakness in your theory yourself:
“I don’t have a straightforward explanation of why this identification also leads to the development of autogynephilia — why the boy begins desiring to be sexually passive and submissive, even becoming ‘pseudo bisexual’ in Blanchard’s terms, when he is originally heterosexual.”
First of all: Most male assigned people do not become crossdreamers. This also applies to those that have repressed their more vulnerable or feminine side to the point you are describing. The great majority of men watch porn. That does not make them crossdreamers. Many men read manga and watch anime. That does not make them crossdreamers.
Moreover, the majority of the male to female crossdreamers I know report crossdreams from an early age, before puberty. Many of them grew up before the Internet and did not have access to the kind of media you describe. Many of them hadn’t seen porn until long after they became aware of their crossdreaming. Some do not watch porn at all. They still dream of becoming women and have sex as women.
And yes, in spite of what Blanchard says, there are also a lot of female to male crossdreamers. They also love anime and manga, but of a very different sort.
All of this implies that there is something else that causes crossdreaming, a factor X that is there from a very early age and that might even be inborn. Your idea of a repression of the “feminine” still makes sense. They are drawn to such comics and stories because they find a language there that makes sense of their feelings. Transgender people, like all others, are influenced by the surrounding culture. If that culture is misogynistic, their fantasies might also be.
Most serious researchers on trans these days believe crossdreaming can be just one of many ways a repressed gender identity expresses itself. This even applies to the DSM-5.
I am surprised that you refuse to consider sexual submission as a natural instinct. Why shouldn’t it be? People in the BDSM community are very clear about this: Do not confuse the sexual instinct of being the receptive partner in bed with social submissiveness. Sexual submissiveness in neither good not bad. It just is.
The MTF crossdreamer may actually be wired for preferring the receptive role in bed (a preference shared by many cis women). This may also explain why some MTF crossdreamers who are primarily attracted to women have fantasies of being penetrated by men or women. The most meaningful parallel is found in the way some cis lesbians play with strap-ons and watch gay male porn.
For some crossdreamers sexual submissiveness is mixed up with fantasies of social submissiveness, as you point out, but I know enough about the fantasies of crossdreamers to tell you that a lot of them dream of becoming strong and independent women, not playthings for men. This is also reflected in transgender literature. Indeed, you will find that most of the MTF crossdreamers who do transition are not walk-overs in any way. (Julia Serano comes to mind. Read Whipping Girl!).
Research into the fantasies of cis women also show that many of them have fantasies of being forcefully taken, even if they would all agree that rape is a crime in real life. Fifty Shades of Grey is a horrible collection of badly written sexist clichés, but that does not stop many women from being turned on by it. You have to distinguish between sexual fantasies and what people think is OK in real life.
Finally: The autogynephilia theory is a collection of sexist and transphobic 19th century stereotypes that have been thoroughly debunked by both researchers and transgender activist. Seriously: Blanchard thinks gender identity can be reduced to sexual orientation! This is the classical inversion theory taken to its extreme. It is scientific nonsense. Read my write-up on autogynephilia here.