Facts like KOF only being popular in a dystopia of a country while the company went bankrupt for its business in other regions, then was saved by rich fans. KOF today is less popular by SF, Tekken, Mortal Kombat, even stuff like Guilty Gear. Not saying it isn't a good series or unpopular, but there are better options for a third party rep.
Also popular series =/= has a good character for smash. Ryu is iconic in a way Terry isn't, Terry seems to be the "I guess he's technically the mascot" type of character. League of Legends is popular too, and Overwatch. Tracer and Jinx would be poor additions though (way worse than Terry but my point stands)