I'm not talking about average smash fans. I'm not sure how did you get the notion that I'm talking about average Smash fans? If I'm talking about average smash fans, then I would talk about Bandana Dee, Geno, Isaac, Dixie Kong, obscure picks that Smash or/and Nintendo fans really wanted to see. I have a feeling that you are trying to throw "your average smash fans" to just dismiss my points about Sakurai wants to focus on more collaboration and new franchises inclusion; and how they dropped Nintendo All Stars from the title.
Smash being the promotional vehicle and Sakurai might want to surprise the fans with favorite are the reasons why I haven't counted out Nintendo franchises YET and I'm open to it as well. There is a reason why few people strongly believe that it's going to be majority of third parties because of Sakurai's comments and President's comment as well.
Basically it seems that it's a smart move to attracts fans by including their favorite franchises' characters in Smash Bros. So both sides would get exposed to new stuffs. Nintendo fans would learn more stuffs about third parties' franchises. And third parties fans probably pick up Smash Bros to play as their favorite character(s) against friends or so. Essentially they would get introduces to those Nintendo characters and third parties but is it completely guarantee that they would pick up the games. Nope but that's a risk they chose to endure. Also if people are going to pay for online services then they would get exposure to Nintendo Online System (NES and SNES).
That's why I think it's pretty smart move for them to making their goal to have Ultimate Crossover for Super Smash Bros Ultimate and Super Smash Bros Special. So it's essentially a special game to have a lot of crossover from many different franchises through collaborations. We will know for sure what would happens with second fighter pass eventually. People are getting their excitements from seeing who would be next characters getting in Smash Bros.
The truth is guest characters are more appealing to casual fans so that's why many fighting games are starting to have those guest characters from another universes or so. But you are right about the points of DLC is promotions both way or so. However at same time Sakurai said that it's a risky business so I presume with his statement that they also expect to make profits as well. They probably want to make profits, not just from characters but from the games they potentially sell to new fans.