To be Fair, The Idea of a Xenosaga Remaster failing profitability Test Is I would say something to consider. I do think Nintendo would have to take that Consideration
However, KOS-MOS is weird that she goes beyond her game, and is more popular character than the game itself. She's been kept Alive by Crossover Apperances, including in the Recent Xenoblade Chronicles 2. Monolith, Who Nintendo Owns, Goes out of their way to License KOS-MOS (and T-LEOS) from Namco into Xenoblade Chronicles 2. Xenoblade 2 isn't the most Casual game like Mario Kart or Smash so going out of their way to do is important to Consider. It shows first the Licensing is cheap
But I think the main thing in KOS-MOS's Favor is that there is interest from both Monolith to Use her, and there's Interest from Harada-San, Who's in a very High Position in Namco, for a Xenosaga Revivial of Some kind.
Sakurai said that Not only does He and Nintendo got to want the Character, but that the 3rd party has got to want the character
Namco is involved with Smash and have shown interest in Reviving Xenosaga, KOS-MOS's Home Series. Monolith shows interest in using the Character.
Because KOS-MOS is Tied to a game like Xenoblade Chronicles 2, Nintendo Can see KOS-MOS as a Character that benefits the Xenoblade Franchise, and Monolith as a Whole. this is because KOS-MOS is seen as the Mascot of sorts of Monolith. I think this is also important because there's more likelyhood of KOS-MOS sticking around than a Character like Rex, since Xenoblade is a Revolving Series, so going with a Character that does keep making Apperances even after her Role in her franchise is over is something to Consider
Nintendo can Benefit from KOS-MOS's Inclusion because she puts more Spotlight on Xenoblade, and potentially other Avenues from Monolith. Namco Benefits in that perhaps this could saw Postive conclusion in next Profitablity test, so there can be Xenosaga Remasters, and that could pay of in the long run. Monolith gets to have their Mascot, and their favorite character in Smash.