Sure. The bulk of my insights about K. Rool as a potential Tropical Freeze Switch addition already are
in that thread. The main piece I’ve tried clarifying in footnotes, and that people unfortunately still incorrectly repeat, is that Sakurai blocked or denied K. Rool from being a bonus boss in the TF port. That was Nintendo, for reasons I am led to believe have to do with letting his return happen on the bigger stage of Smash. Though one person suggested that Nintendo simply did not want Retro to bring back characters in the port who weren’t already in the original game, so…
I do want to underscore that Retro was never the obstacle toward Kremlings returning. Given all the other fan requests Retro granted in the jump from Returns to Tropical Freeze, it’s curious that, according to these sources, one of the first things they tried to do with the TF port — for which Kensuke Tanabe is credited just with a “special thanks,” rather than as the producer, as with the main game — is to try to bring back K. Rool. Retro was always in our corner, they just had to play with the hand they were dealt as a Western studio under Nintendo’s purview.