i don't see any reason why it can't happen. cargo cults like the above seem to be a good example of actual people who become worshiped as divine beings.

Prince Phillip, while worshiped as a savior deity, doesn't fit the Rank-Raglan hero type so far as I'm aware. That's a much more specific reference class, which Carrier considers relevant for setting the prior probability for Jesus.

Cargo cults are an interesting thing for you to bring up, for several reasons. First, the Prince Phillip cult is a bit of an anomaly, as most cargo cults produced fully historicized and yet fully mythical messiah figures, like John Frum and Tom Navy. These people never existed, but the islanders fully believe they did. Second, even in the case of Prince Phillip, in no instance was the savior god of the religion, even though portrayed from the start as a historical person doing things on the island, ever actually the founder of the religion, because they either didn't exist or (in Phillip's case) didn't have anything to do with the founding of the cult.

suppose we just didn't know, prior to the argument, that colonel sanders was real. what would we assume, based on the other corporate mascots? would this still be a good argument?

If, for instance, somewhere in the future the evidence for Colonel Sanders' existence were lost, and all that the historians of the day had to go on was his presentation as a corporate mascot, they would have to conclude that he probably didn't exist. And they would be entirely reasonable in doing so. They would be wrong, but that's why it's a probability. We can always be wrong, and must be willing to update our conclusions if new evidence comes along, but we cannot be blamed for basing our conclusions on the evidence we do have.

skepticism is a good thing; skepticism in the face of a reasonably solid argument is another.

That's a point on which I suspect we're going to differ. I'm with Raphael Lataster on this; here's a point he makes in his recent book:

I find it quite amusing when my detractors point to the seeming implausibility of mythicists’ theories and to apparent errors in my case for Historical Jesus agnosticism, when the justification of agnosticism is already made obvious by consulting the people arguing for Jesus’ historical certainty. Forget what I have to say. Forget the more aggressive overtures of outright mythicists such as Richard Carrier, Robert M. Price, David Fitzgerald, and Acharya S. Simply peruse the sources for yourself. Do that, and also hear from the historicists how they ‘prove’ Jesus’ existence. If the case for Jesus is unconvincing, then agnosticism is already justified. You needn’t bother with the various active cases against Jesus’ historical existence, many of which honestly sound ridiculous. For your convenience, I condense my years of doing just that into this 400-odd-page book.

The arguments for historicity are just bad. It's not a solid argument at all. For instance, in Did Jesus Exist?, Bart Ehrman makes use of hypothetical sources quite extensively, suggesting that they all provide independent witness, and thus "prove" Jesus existed. Lataster again:

I simply cannot find enough negative superlatives in all the thesauruses in all the libraries in all the world to describe the complete and utter ridiculousness and bankruptcy of Ehrman’s approach: The generally unreliable, untrustworthy, and fiction-filled Gospels can occasionally be considered excellent sources of objective and accurate historical information because of their foundational written sources, which do not exist, which contained many fictions if they did, and which cannot now be scrutinised for authorship, age, genre, intent, and so forth. These hypothetical written sources are themselves based on oral traditions, that also cannot be scrutinised, that changed over time, and that may well have been made up whole cloth. Therefore we have conclusive proof that Jesus definitely existed. This is enough to make supremely logical analytic philosophers suffer aneurisms. In what universe can this be considered good history, and good scholarship?

that most other gods are entirely mythical isn't actually all that relevant.

This is really a question of epistemology. If you look at things from a Bayesian perspective, it has to be relevant, because you can't pretend we don't know that. If, as you claim, the hypothesis of historicity does provide a good explanation of the evidence specific to that question (which I don't think it does), then it would be the case that the posterior probability is high, but that would not entail that the prior probability was not low, or that the low prior didn't enter into the calculation.

A classic example for Bayes' theorem is testing for drug use. Suppose a drug test is 99% sensitive and 99% specific. That is, the test will produce 99% true positive results for drug users and 99% true negative results for non-drug users. Suppose that 0.5% of people are users of the drug. If a randomly selected individual tests positive, what is the probability that he is a user? When you run the numbers, it's about .332, a little better than one in three. A person who tests positive is more likely to not be a drug user than to be one. Why? Precisely because P(user), the prior probability of the "tested person is a drug user" hypothesis, is so low. Even though the "user" hypothesis fits the evidence quite well, its low prior probability of being correct is highly relevant.

You can, of course, overcome a low prior with really good evidence. Going back to our earlier example, the prior for Colonel Sanders is quite low, but the evidence available for him is so unlikely to exist if he were fictional that the posterior probability is extremely high. It would be easy for us to have that evidence for Jesus; we have plenty of examples of the kind of evidence that could survive for an ancient person that would be convincing. Say, for instance, the attestation we have for Spartacus. We just don't have that evidence for Jesus, and the evidence we do have isn't nearly good enough.