If you really like the narrator telling the story idea, maybe you could put snippets from his version of the text at chapter beginning to bring his voice more strongly into the series. Just a thought.

At this time, the most transparent form is Third Person Limited Omniscient, where you describe the feelings, thoughts, perceptions, and experience of a given character from the point of view of a neutral observer that experiences the action only as seen by that character. I could give an exposition of why this is so, and what advantages are gained though the use of this device, but that would make this a very lengthy post indeed. Instead I will simply explicate some of the reasons and requirements for using First Person.

First Person is a form that has largely gone out of fashion for two reasons. Its primary value is in maintaining the illusion that the story actually happened and is being retold by an eyewitness to the events described, which is no longer considered a necessary element of maintaining suspension of disbelief. With the decline in necessity for creating a "virtual document" in which to tell the story, this form has been largely abandoned because it imposes strict limitations on the narrative, prevents deep personification of and identification with the POV character, and is very difficult to carry off effectively even for the most talented writers.

However, your second notion, that of telling the entire narrative as it might be retold by a later (also fictional) character, is full of possibility. First you should recognize that in telling the story this way, you require a "First Person Narrative Frame", wherein the narrator character has particular (some explicit and some implicit) reasons for writing the narrative. Therefore, it would seem appropriate to have this character write a preface, a prologue, and likely an apology, in addition to the epilogue.

You should also keep in mind that the language used throughout the narrative must conform to what would be appropriate to your fictional narrator. If you slip in anacronistic vocabulary, usage, or terminology anywhere in the story it will break the mood far more severely than would be the case otherwise. Also, you have to make sure that the literary forms, including the conventions for POV and plot structure, conform to the fictional setting of the narrator character, not the conventions of this time.

Also important, but less obvious, is assigning values and cultural assumptions to the narrator character that are consistent with the milieu from which he or she is writing. For instance, you might need to invoke a lengthy "justification" for the hero doing something that would be contrary to the mores of that culture, like borrowing money, or eating meat after dark. By the same token, actions that were acceptable in the narrator's mind, such as killing someone over an insult, or setting fire to a forest, would pass without any conscious attempt at justification on the narrators part. I say conscious because in order to appeal to a modern audience you will need to find some way to make it clear that these actions are, in fact (or to be more accurate, in your fiction), fully justified. You just can't have your narrator do so consciously.

Instead, have the historian write the epilogue because the historian found the story and is acting more as an editor and/or translator of the story.

That way you can keep your omniscient narrator (and have that narrator be anonymous, if you like), while still having the commentary at the end by the historian.