Sounds nice. I think with Seasons, the gift giving will comeback and can plan events ahead of time and can also sort of create bachelor parties probably (just need dancing on the tables and sims affected by 'juice' again), so that won't be need or at least not as something new but enhanced with new options. We do need slow dancing and have some more CAS and objects for wedding. Also new cakes and arches.
Maybe they can hire a band *hint hint* (I want bands back!).
If we can make it as a game pack, there can be a lot more to it, including a new lot to hold weddings and receptions, traits, etc...sims that get left at the alter depending on their trait could either be really happy or become extremely sad and can possibly die (such as from a broken heart; but it depends on the specific traits a sim has as their moods will vary). Sims can have a midlife crisis.
There is just so much you can really do. Maybe it could be a part of a full generation expansion since a lot of life stages sort of need more to them. Like they can film the wedding and elders can remember and think back on it. Teens can go to prom.
There could even be a wedding/event planner career or set up like a bridal shop as a retail.