What do you want out of a Romance Expansion?

I've stated this before, but here goes - the option to lock two of my Sims into a relationship or marriage, essentially preventing them from responding to a third Sim's flirting just because the two of them has watched a romance show on tv. But if a reward trait could solve the issue better, I'd be all for it. Not sure how it would work. Would your Sim be immune to any flirting sans from their partner unless the player personally initiates it. I'd take anything to keep at least some of my Sims faithful.

Was gonna suggest more couple activities, walking holding hands, playfully jogging together, having a picnic, piggybacking (non-romantic as well), hand-holding when sitting next to each other at the table (unless they're eating) and hushed conversations either standing or sitting. Was gonna suggest two people on a waverider and a boat too, but I guess they wouldn't interfere with other packs?

Different kind of wedding rituals/ceremonies, as someone suggested, would be great as well. Maybe an added section in the clothing department for wedding clothes, a variety of them depending on which part of the world your Sim hails from or wants to belong to.