The two characters really aren't comparable. Rosalina rules over Galaxy's hub area, and she appears all throughout the game's storyline -- she gives Mario his Luma, she's in a bunch of important cutscenes, and she even has her lore fleshed out through a storybook. Pauline is important to New Donk City, but that's just one of Odyssey's dozen-plus kingdoms. She means nothing to the game as a whole. Odyssey is the Mario, Cappy, Peach, and Bowser story. And unlike Rosalina and Luma, Pauline doesn't have a relationship with Odyssey's central mechanic, Cappy. I definitely agree that she'd feel forced, and I say that as someone who likes what Nintendo did with her character.