I would love a celebrations pack! Also, it would be nice to somehow sort the weddings out so they worked a bit better. I always feel like they're kind of rushed. I'd love to be able to make it a longer process with goals, sort of like a pop up like how they do for parties and the like, and for the wedding to involve both sims, not just the one planning it. The pop up could stay up till you get married with a checklist, such as ...
Plan your wedding!
- Archie's Friend of Honor
- Betty's Friend of Honor
- Wedding Venue
- Cake Topper
If you choose to plan a wedding, you can have a moodlet 'wedding planning'. If things go down to the wire, you could get a moodlet called 'Bridezilla' (for men or women) and they get stressed out and have breakdowns xD
I'd also love to see a larger footprint for wedding arches. If you chose a maid of honor/best man/whichever, they could have a place to stand as well. It would be awesome to be able to choose your colors for the wedding as well, so that when the wedding started, the wedding party changed their clothes, too. This would actually work well in the way that retail and restaurant lots choose their uniforms and such.
Just a few ideas to throw in there :)