Edwin’s tunnel vision/problem solving = I make an offer for Portia’s hand, she remains helping me at court until I leave, then she can be free to do as she pleases
The reality = they’d be married
I am a sucker for marriage of convenience, Portia and Edwin are both coniving and playing 4D chess around being together so it makes sense. Edwin wouldn’t want her to marry some gross old man and needs her help (wants her himself) Portia wants to retain her freedom and feels she can push Edwin around (wants him for herself)