Ambiguity has been a recurring keyword for me throughout this research so far, and when viewed in practical terms - how far can we go before it is assumed a truth of either x or not x in a form or persona? Before a form stops being ambiguous and can be accepted for what it purports to be, at least on the surface?
For the sake of neutrality and to avoid getting mired in gender identity matters, I'll frame this discussion in terms of the old saying regarding that which looks like, and walks like, a duck. The duck metaphor or stand-in reduces things to a less ambiguous level and helps us to see at which level taxonomies and definitions apply, or cease to apply, and why this may be.
Logically, if it looks like a duck, walks like a duck and quacks, why should we not allow it to be described as a duck? Must we insist upon analyzing it inside-out with regard to its 'apparent' versus its 'actual'/underlying duckness (or lack thereof - usually defined in taxonomical terms of reduction, or its consistent similarity to other entities which have all been previously rubber-stamped with a 'genuine duck' seal of approval, by the hand of someone who is not a duck themselves, but who defines for others whether or not they may be allowed to be perceived as ducks - as opposed to swans, emus, or archaeopteryxes?).
In reality, we accept the following image as being splendidly representative of duckhood:
We also, from a very young age (that is, pre-adult judgement) have no problem whatsoever with identifying the following as a duck, either:
Or even the following - a thing made by hand, with only superficial resemblances to duckhood (can't walk or fly, lay eggs, quack, etc.), yet which is convincing enough to attract real members of that same species:
To then waddle on from the duck metaphor, why can we universally assume that the following image represents an entity we unthinkingly define as "she":
and, paradoxically, also this:
yet are unwilling or unable to do so with regard to this:

It follows, therefore, that a few hundred thousand tonnes of metal or wood is perceived by many as more inherently female than a living, breathing person (who may or may not have the exact same outward biology as an assigned-at-birth female). The connection (or disconnection) is, I perceive, more than semantic or visual - it operates on a gut, instinctive, and emotional level, wherein emotional attachment is more easily transferred to an object/piece of machinery under one's control than a human being capable of the same emotional responses and sensations as the one who does the naming. Perhaps that is the keyword in all this: control, and the implied power/jurisdiction which is invested in the (usually male) owner or commander of a vessel over that technological/mechanical interface, but which is denied in the case of an actual person which is too *similar* to the protagonist, too much like himself, too incapable of yielding to commands on account of shared biology (in the sense, of course, that what is popularly described as "feminine" tends to be identified also, variously, as "soft", "yielding", "submissive", etc. - as witness the recurring tropes of hyper-femininity inherent in the "forced feminization/sissy" area of pornography and role-playing - something for which I have no stomach, and am aware of only for its intersection with the trans* spectrum on the level of cross-dressing and female embodiment fantasy theory. (NB: Despite its appearances, I view this more as a subset of extreme masochism rather than any clear or defined actual gender identification, as it is predicated on the idea of "feminization" representing submission, passivity, and at the extreme end, sexual and other forms of abuse. Thus the debates of how far down the spectrum we may go before we start accommodating fetishism as a form of gender diversity at such public events as Manchester Sparkle - which is a discussion for another post perhaps, but one I have seen argued repeatedly in the past.)
What I'm evidently pushing towards with all of this (but still circumnavigating somewhat) is a code of semiotics and signifiers: whether of the "C'est ne pas un pipe" art-historical variety, or the visualization of Sign-Signifier-Signified - something along these lines, as I see it:

The argument is far more complex than simply that of a person exhibiting the outward signs (costume, behaviours, overall appearance) of an other, but in how far - intrinsically - that exhibition can be said to make them analogous, or identical, to that other - a situation dependent upon not just the quality of the performance, but also how well that performance constructs the essence of of the other in the minds of observers. Putting on a police officer's uniform doesn't make anybody a police officer, even if they have knowledge of laws and have sworn (personally) to uphold them, and spend their time going around protecting the innocent. What constitutes a genuine police officer in a society is a far more complex set of relationships, histories, connections and requirements, of course. But in the minds of many citizens, the would-be officer could be just as much - if not more so - a police officer as the 'real thing', especially if they had only positive, personal experiences from an encounter with such a person, who could even come across as friendlier, more approachable and more helpful than some genuine representatives of law enforcement. In such a case, the impersonator may be said to be modelling the 'ideal' of a police officer, presenting the positive side and downplaying the negative associations which have become increasingly public in recent years - in which case, and if everybody involved benefits from the encounter or the experience, where's the harm? (Leaving aside, of course, the realities of accountability, legal obligations, public trust, etc.).
Let's leave the ducks in the pond and cut to the gender case now.
“Men, contrary to the fantasy of the transsexual, can never, even with surgical intervention, feel or experience what it is like to be, to live, as women. At best the transsexual can live out his fantasy of femininity—a fantasy that in itself is usually disappointed with the rather crude transformations effected by surgical and chemical intervention. The transsexual may look like a woman but can never feel like or be a woman. The one sex, whether male or female or some other term, can only experience, live, according to (and hopefully in excess of) the cultural significations of the sexually specific body… This gulf, this irremediable distance, is what remains intolerable to masculinist regimes bent on the disavowal of difference."
Herein we hit the dilemma that may be the crux of all this research: how much of identity - and gender - is merely appearance, whether biological (natural or otherwise), facial, sartorial, etc.? I appreciate completely the often-used argument against the transwoman-as-woman, that one who has not been born a woman, experienced the growing up stages of puberty, menstruation, social and cultural and conditioning etc. throughout their entire life on a daily basis that define one's place as a woman in the world, cannot be said to be truly - in any rounded, socio-cultural way - a woman as one who has (and one of the reasons why I spend most of my time discussing in-betweenness, non-binary being, and third-gender, rather than pushing the transwoman-as-woman line which, to me, can have potential problems with relation to furthering the strict gender binary, and allowing the continued encoding of persons as either/or). That does not mean such a person has no claim to womanhood whatsoever, for upon gender reassignment, it is expected that they will then experience the responses and interactions common to one of that gender and in that position, with all the positive (and negative) attributes that such status brings.
A lot of this seems to echo Jean-Paul Sartre's ideas of essence, true nature (and its construction in the minds of others), and the very famous example of the waiter who, in trying too hard to project publicly his waiterly credentials, is seen to be merely 'playing' at being a waiter, rather than working hard on the true fundamentals of waiting on tables. Yet can we say that Sartre's waiter is less of a waiter, than Daffy is a duck? After all, the waiter is employed in that role, receives a wage suitable to that position, and will be referred to as a waiter by his employer, colleagues and the public. Daffy is not an egg-laying creation of nature, but a series of squiggles and dots on acetate sheets drawn by talented cartoonists. And while he may talk like a duck, he doesn't really walk like one - his legs aren't short enough.
That's all for now, as I think I need to push my nose back into semiotic theory again and figure out where I take it from here. The question there, however, remains: Structuralist, or Post-Structuralist? I've spent time in both camps in the past, but now it might be time to choose a side.