I think what u did is great and could well be correct but u forget that there has been changes in part 1 and that kakashi is the one who said the sharingan is descendant of the byakugan and kakashi is the same person who said the rinnegan is a mutation and the sage was a fairy tale and we now knw that was wrong...and I think the elder son just had a rinnegan and not some hybrid rinnegan/ byakugan because as we knw ancient civilizations draw things much differently than we do now and that there drawings are not as detailed my point is that the elder sons eyes was drawn like that because of the times and era...it's not lime that was an actual photographic picture because there aren't barely pictures in naruto now and if the uchiha descendant from the hyuuga then it would be hyuuga vs senju and maybe hyuuga elder vs hashirama instead of Madara vs hashirama
But what u did is amazing and I applaud u for it and u very well could be correct but the thing is for right now all we say and show are just opinions until kishi clears it up