I love that you have decided to try your hand on a TOS-era story. It does not seeem to be a very popular era to write for and those who do prefer an entirely different approch.
But I have to say that I was a little disappointed that you decided on such a well-tried opening for this series. I know it makes sense, the captain gets his ship, we meet the crew, the crew meets the crew ... and so on. But it is a formula that, I believe, could use a little variation.
Having said that, this is of course only the beginning, and you could go virtually anywhere from here.
I hope that you will be able to set this apart from more modern oriented fan-fic and perhaps even capture that classic, often campy feeling of the TOS era.
I am going to follow this with great curiosity.
Why do you call your ships destroyers? It sounds very militaristic and I didn't think TOS was.
Aren't Miranda class ships mostly associated with the movie era of Trek? I say that because I remember that their design was based on the movie-era Enterprise not on the TOS Enterprise. I might be mistaken on this one.