Sort-of-Reluctant Princess: When?

I'd been rolling this concept around in my mind for a while, without really getting anywhere, and figured I'd try to get some advice on where this would be a good fit in terms of historical plausibility (albeit on some sort of parallel world).

It's a point in time when monarchies/empires are more or less absolute. (There may be a king-in-council type of arrangement, but the king is the one with the power and the major armies are under central command rather than loyal only to a local noble.) The most powerful nations can be thought of as Eastern and Western empires, with (as usual in stories on this side of the divide) the West being the good guys. I don't know whether it's going to turn out that way geographically, but that's an easy way to look at the concept here.

There's a whole lot of unaffiliated area, thought of as less civilized by the two empires. Both sides are looking to expand their fields of influence, although the East goes for absolute conquest whenever possible and the West is willing to accept affiliated third-world type states. (Not sure whether those have to profess fealty to the Western emperor, or can simply ally with them.)

Where we're going with all this: the Western royal family -- a king, queen, 16- or 17-year old princess and a crown prince three years younger, are traveling to someplace more or less equivalent to the eastern African coast, deciding that a full-blown royal visit is the best way to fold them into their alliance. To do so, they're traveling on some sort of conveyance -- horseless carriage or horsedrawn coach, depending on the tech level. They're the focus of a caravan, which includes soldier types and merchants who see this as a big opportunity to expand their businesses.

The king's brother-in-law, who has royal credentials, so to speak, since he and his sister the queen are from a noble family, is serving as regent in their absence. If they all were to die, he could almost certainly claim the throne since there aren't any closer relatives.

And that's where things are headed. The royal vehicle is sabotaged and falls off a cliff to certain death -- there's no way any of them survived, though the bodies either can't be recovered or have been mangled beyond recognition. And there were others in there: the driver or chauffeur and some servants or bodyguards. But what they don't know is that the son was in a following vehicle, being educated, so to speak, by the daughter (about the princess's age) of one of the merchants.

The prince, once he makes his presence known, and at least some of the soldiers strongly suspect the regent and his sons are behind this. (I'm not sure whether they actually capture the guilty parties, and if so, whether those people confess without being tortured into saying what they all want to hear. Seems too much to expect one of the regent's sons to have done the deed personally.) But there seems little doubt that the entourage needs to turn around and head back quickly before the regent can consolidate power.

The trouble is that the prince is underage, and the presumably evil regent would almost certainly remain in that role if the prince came back. The latter's life expectancy wouldn't be very long under those circumstances, either. But there's an alternative (which a lot of you have undoubtedly gotten to by now). The princess was of age, and if it had been she who survived, she'd become queen and could expose, depose and then dispose of the brother-in-law and his family.

The prince looks enough like his sister to be able to get away with it initially, though any of her ladies-in-waiting and other close palace personnel would see through the deception instantly. Further, he's not going to be able to keep up the masquerade as he continues to grow, and even if he could, his destiny would probably be to eventually marry a nobleman for political reasons and very likely give up some or all the power to the new husband.

So the prince can't conceive of trying to rule the empire as a woman for the rest of his life, even if the sex change didn't bother him . But there's another solution: they'll announce that both the prince and princess survived, that the prince is remaining in hiding for his own security until he's old enough to legally take over, and that the princess is assuming command as the new regent, not the queen.

Complications, of course, ensue, not least because the deposed regent, convinced that the Eastern empire was stronger than his, had made arrangements wth their emperor to withdraw his forces and monetary support from the buffer state between the two and allow the empire to conquer it, in exchange for the emperor's personal assurance that the West's own borders would remain safe. (And to make sure, he'd build this big, beautiful border wall...sorry.)

Anyway, as I've done once or twice before with stories that never materialized, I've written the whole setup here in the forum section to try to get to the point that I was looking for advice about: where in a history resembling ours could this fit? I don't want to put it in the usual medieval fantasy world, because that would lead one to expect magic or some deus ex machina to show up, and I'd like it to be clear that's not going to happen. A very early 20th-century tech level might make it work, except that communications might be good enough in that world to forestall a lot of this; also, the power structure here strikes me as much earlier than that. I've never tried to write steampunk (and not really read any: I did watch The Wild, Wild West on television in the 1960s, which sort of qualifies); that could push it back one generation, which I'm not sure would help.

Before someone points it out, if this is a fantasy world that I'm defining, on a planet with features that don't even have to physically resemble Earth, the tech levels can be anywhere I want to put them regardless of the rest of the situation. But I think there needs to be some consistency there, and I'm not finding it.

Anybody want to comment?

Eric