You could argue that the first rule was manifested in Brawl. Remember, in Brawl the only SEGA content was from Sonic, and the only Konami content was from Metal Gear, with not a single trace from any other franchise from those respective companies, compare that to Smash 4 and Ultimate, were the companies were more lenient. Character from the same company showed up and some franchises got representation in non-playable form (Monster Hunter's Rathalos) but if this was like 2009, you would be hardpress to make an argument for Simon or the like because people would shut you down with "ONE CHARACTER PER COMPANY" and nothing in Brawl pointed against that argument. To you your fan-rule of 3rd party westerns may seem reasonable, but that's because so far it points to your favor, just like in Smash prior to Ryu's reveal regarding the "one per company" rule fans had.
Same with the "3rd Parties must be icons" fan-rule. This one was the reason as to why the only characters that were prominent in Smash 4 speculation that were third party were Mega Man and Pac-Man, anybody else was almost a no show or got heavily scrutinized. Back then if you argued about Shovel Knight, nobody would tell you "NO WESTERN THIRD PARTIES", they would instead say "THIRD PARTIES MUST BE SUPER INCONC MAINSTREAM POP CULTURE FACES" (in a way it's almost like people moved the goalpost regarding Shovel Knight, but that's another topic) If we go back to E3 2014, Sakurai made a big deal of these super important gaming characters (Mario, Sonic, Mega Man and Pac-Man) and there was no dobut in many people's mind that any other character must be on the same standard as these 4 (which admitedly, Ryu and Cloud follow up nicely with those 4, even if the former broke the "One rep per company" fan-rule and the latter broke "Must be heavily tied with Nintendo" fan-rule completely)................and then Bayonetta showed up and threw that fan-rule in the trash (Bayonetta's games don't sell even a fraction of many of the other third party franchises in Smash, and Sega didn't even wanted to fund the seuquel so Nintendo ended up doing it instead, no matter how you slice it Bayo doesn't even compare to many of the other third parties in Smash when it comes to legacy, popularity and recognotition)
Fan-rules are nothing but the manifestation of a pattern that only exist as soon as fans notice and is Destroyed the moment they start it using it as a guideline for characters. Your arugment of Western Third Parties boils down to "IT HASN'T HAPPENED BEFORE SO IT CAN'T HAPPEN NOW!", which is laughable.