Another psychological element in Notorious missing from MI:II was Alicia’s past with both men and alcohol. Two things which greatly complicated her already intricate relationship with Devlin, her undertaking of the assignment, and consequently Devlin’s last-second rescue.
Devlin built a relationship with Alica and then, once she was sober and ready to be monogamous, betrayed her by asking her to be a spy, marry another man. So later, when they’re on the park bench Alica allows Devlin to believe she is off the wagon because she feels he’s treated her like a whore, and Devlin, who has treated her poorly in order to deny his feelings for her, is unable to realize she’s been poisoned.
Throwing Ethan and Nyah into bed as a shortcut created a purely sexual chemistry instead of a psychological one. What may seem like a minor change actually left out the impetus for the final act and the wonderfully tension-ridden payoff. The relationship in MI:II becomes a cringe-worthy MacGuffin.
But hey, there were some doves. And things blew up.