Lets say that persona 5 comes for switch as joker (and a stage, spirits, amiibo from the game) is a newcomer DLC. And lets say that this model keeps going, every DLC character represents a game that is coming to switch, for instance: Gerald on smash, the witcher on switch; sora on smash, kh3 on switch; travis on smash, no more heroes 3 on switch; FE 3 hores main character on smash. 

Wouldn't be a good model (for consumers, developers and Nintendo) to offer a DLC code of the smash character with a copy of the correspondent game?

At first seems that they wont make money, because they will not sell as many fighter passes. But in the consumer perspective, if you have the game, you wont need to buy parts of the DLC (you pay only for those you don't buy the game, if you want all DLC). For the developers of these games, consumers may have more incentive to buy the games because is other way to earn the DLC, where you also get a game to know. For smash, players who don't have smash but buy one of the games will have already the DLC of smash, and may like to buy smash bcos will have already extra content of the game. For me, it seems to be a win-win-win scenario that helps the games on switch, help smash sell more copies instead of fighter passes and consumers will love. Thoughts?

Or... they could have people buy the games and pay the DLC money!

Anyways in all seriousness not every dlc fighter in Smash is going to correspond with a new game so this wouldn't work. (even if one does like Persona 5 comes to Switch, the release dates of the fighter and the game would likely be way off from each other as the games are going to take more time to make than a fighter) Nintendo isn't going to force every 3rd party to put out a specific game on Switch if they want their fighter to be allowed in Smash.

Honestly seems like a good idea. The PS4 version of (insert game here) may look better but the switch version comes with portability and smash dlc