Bethesda in Smash discussions? I can contribute to that!
I used to be really anti-third party. I had no clue who Snake was back in Brawl, and the only one I accepted was Sonic because of the whole rivalry in the 90s that defined dueling companies. Everyone likes to talk about other mascots, but none of them are the kinds of household names that Sonic was. Heck, the first time I heard the name "Rayman" was when the trophy was announced for Sm4sh.
Now I never thought about having Bethesda stuff in Smash since I did prefer everyone to be one a Nintendo console first. I didn't even consider Dovahkiin until the Switch announcement trailer when they announced a port of Skyrim - before that, Skyrim was a game for consoles and high-end PCs, and Nintendo was the kids' and nostalgia console that sometimes slipped and made weird choices like Bayonetta that should have been on the 'big boy' systems.
The Switch changed that. Nintendo is trying to market itself as more than 'babies and man-children' by showing that they don't just print millions of Mario party games and Pokémon, but that they can also be a gaming console for everyone. And how did they show that? Skyrim. Breath of the Wild was a phenomenon - it's not like other Zelda games or standard JRPGs...it actually feels more like a Western RPG than anything else. But it's still a Zelda game, and there are plenty of elitist gamers who consider anything Nintendo to be for kids. So what was the second game they showed off? Not Mario - it was Skyrim, which is one of the few western games to have gotten great ratings in Japan (How many games have achieved 40/40 in Famitsu, particularly western games?) and effectively shut up most people who don't think of Nintendo as a proper console maker.
That's what I consider Bethesda's contribution to Nintendo history. They use a major western developer known for massive, sprawling, lose-yourself-for-hundreds-of-hours games to show that they can do what the other consoles do...but they can do it portable as well. Remember Sony tried to make things portable with the Vita? That didn't go over too well...but the Switch is another story.
Now Bethesda's said that they intend to continue considering Nintendo as partners, and they've released several Switch ports of their games by now. But I fail to see how Bethesda is less acceptable of a company to work with than others at this point. True, most of Bethesda's games incorporate heavy violence (which is easily toned down, ask Snake) or include avatar characters without a canon appearance (but they've gotten in the habit of a uniform look for marketing, see Robin and Corrin). Bethesda's games are pretty high on the iconic scale as well. I know I'm one of the only people around who advocates for Dovahkiin, but is should mean something that loads of people on these boards haven't played it yet still recognize the look as "that dude from Skyrim" despite that being the worst armor in the game.
I can't really speak much for Blizzard, but again I know a lot about the Overwatch characters and half of their names and even some of their abilities, without even knowing anything else about the game beyond "isn't it on online FPS?" Should speak to how iconic that is.
If I had my way, I totally think Dovahkiin could fit excellently in Smash. There's only one sword/magic fighter, and Robin's abilities don't even come close to the dragon shouts that Dovahkiin'd get as specials with the possible exception of a sort of fire blast. Plus, BotW seemed to take a few cues from how Skyrim played, and then Skyrim added an update for the creation club that added temperature-based survival (like in BotW) and even had some special Zelda items in the Switch version (and added an eye color so you could make your player character Link). I'd love to see the two of them cross blades in Smash, and with all of the dragons in the cast (Corrin, Charizard, Ridley, and now the Rathalos boss), it's only be more perfect.