The show did present a general atmosphere that suggested the Fire Lord usually has to be a bender, with the "superior element" talk, the idea that taking away Ozai's bending is enough to neutralize any threat he presents, how Zuko automatically was presumed to suck because he was less good at bending that Azula, etc. If any nation is going to insist on a bending ruler, it'll be the FN. Which makes me wonder if FN people will be presented as having a different attitude to the anti-bending revolt than people from nations where bending wasn't emphasized that much.