As far as we can tell, the tribves makes it fresh and appricated to experience Rhun again ^^
Númenórean Dynasties! ...sounds like a soap opera
"
The Dwarves and the Beautiful"?
"
Anorien"?
"
Dol Amroth Watch"?
I'm never against outside ideas, for blanks not the least, as long as they fit the overall design and atmosphere of this version of Middle-earth (that naturally tries to be faithful, with a lean against the Dark Age design rather than high fantasy), but when there're lore sources those as a rule prevail.
That was quite an interesting story pitch, as it expands the complexity of arrival of the House of Elendil to Middle-earth (which is quite striaght foreward in lore, sometimes I sometimes wondered over, if also because of a long history build up excuses it), and adds more tragedy, quite in the spirit of Tolkien.
Three reasons we won't go that path however. Not only becasue 1) the only reference about them indeed made clear they are King's Men/BNs, but also because 2) that would feel very unfair to the BNs, as it makes two of only four known individuals in history suddenly no longer real BNs, as well as our only two post-Akallabeth from the Second Age, and lastly because 3) it is thematically far to alike the Castamir and the rebels-story line in the Third Age.