JOJONumber691
You're going to be continually let down if you keep viewing "ease of collaboration" as dealbreaker. At the most extremes, the likes of Disney and Sony, sure. But what about the previous six third-parties makes you think Nintendo opts for the simple acquisition? Two were from new companies, two were from Square, two were western (and from a competitor), all except Terry seemed to involve multiple parties when you consider the music/artwork.
At the point you have Sega, Capcom and Namco on board, you're set for third-parties for several titles. Those companies have a wealth to themselves. But Nintendo doesn't rest on its laurels and mine the same developers over and over as much as they reach out to new ones constantly. And that doesn't even touch on the big companies that have been involved only to the extent of supporting content. Nintendo is not afraid to play the field.
There's no good reason to consider a company like Activision off the table, even if no further western characters arrive this time.
Also, Activision-Blizzard doesn't own Riot. Tencent owns Riot.