I don't think the lions make sense if history didn't go the same way, If I remember correctly they each represent a holding of the angevins(spelling), one for normandie, one for aquitain, and one for england, I also don't think if Harold wins he should be faced with a rebellion, winning against such a large invading force would only have reaffirmed the nobles current stance at the time, that england needed a warrior, not a child, you must remember that england was more of a elective monarchy, akin to the scandanavian way of ruling, so the child really had no right to rule, other then the fact his father was king.
England was much more like a "Gaelic monarchy", in the sense that while it is true the nobles "elected" their Kings, it was presumed and more or less mandatory to always be a previous Kings son. Harold is the
only exception to this I know of and this is for a complicated and exceptional set of reasons.
The first reason is obvious, the throne was in a tenuous position at best and needed an older, experienced warrior to defend the throne. For this reason I think Harold was more or less a "regent for life" for Edgar. By no means do I think Harold would have been able to will or even convince the nobles of England to have one of his sons or relatives succeed him. His house was universally reviled, which brings me to the next reason.
Harold and his father before him had undoubtedly schemed and bullied his way to the throne in England's darkest hours. While I'd prefer not to slander the name of a man who has long since been dead honorably in battle, he by no means is the heroic character romantic psuedo-historians make him out to be and every bit as "dubious" of character as William was.
Example, Edgar's father and presumed heir to the throne, Edward the Aetheling/the Exile was almost certainly murdered upon coming back to England. We can't truly prove who did it, but many then and now suspect that Harold and his ilk had something to do with it, a theory I most certainly believe.
I will amend what I said and instead suggest that while Edgar should a claim to the throne and maybe even a non-historical title (I'm certain many titles in Anglo-Saxon England in the earlier start date will mostly be fictional characters and they also did this for certain important figures of the Norman conquest in the original), he shouldn't always revolt, certainly not so soon after the game starts.
However; he most certainly should be Harold's heir (certainly not Harold's children) and if Harold/the player changes the succession law, a rebellion most certainly should start. One should remember that the Anglo-Saxons were a very unstable/unruly bunch when it came to matters of power.
The Great