We don't think the untangible "flavor" of Star Trek is so inextricably bound to the original actors...
I think we're just gonna have to agree to disagree on that point. The argument about legendary characters like Holmes and Superman has been made before, and the difference is that characters like them originated in another medium and were adapted onto the screen, thus giving each actor a standardized point of reference on which to base their performance. As much as I like Jeremy Brett's version of Holmes, Conan Doyle wasn't basing his characterizations of Holmes on Brett's performance.
Conversely, the writers of the original episodes, after the first few, were basing their characterizations of Kirk and the gang on how Shatner and the gang had interpreted those characters. Even though Spock didn't act quite like himself in the earliest shows, Nimoy still put in a lot of time and effort developing the character beforehand and figuring out how he should be played. In fact, according to an account from the book Star Trek Lives!, Leonard Nimoy essentially directed the pivotal Spock scene of "The Naked Time," which so elevated the fans' appreciation of him. A large part of what the characters are is due directly to the actors that played them. There's just no way someone can say they're interpreting Kirk in a vacuum from how Shatner interpreted him. Kirk was defined by how Shatner interpreted him, and therefore, they are inextricably linked.
Fundamentally, this really isn't the same as Hamlet or Superman. The only "real" Superman is the one in the comics. Everything else is an adaptation. The only real Holmes is in the original Conan Doyle conan. But the only real Kirk is William Shatner, and everything else is based on his performance. If neither the way the actor plays the role, nor the way the writer writes the role is based on Shatner's interpretation, then it is, in fact, not Kirk.
I don't know, I'm not trying to be antagonistic (although I may be failing again); if this is about paying homage to a great show that you all love and cherish, then that's something I can appreciate and enjoy. It's not the same, for me, but I could still watch it on the level that these are fans who are realizing the dream of being a part of Star Trek, and I can vicariously enjoy that experience. But if this is really about believing that this is as good as the original series, then, to be honest, I would find that quite arrogant (if that were the case).
Anyway, I will watch "In Harm's Way," and try to keep an open mind.