I think you could wear a cardigan over the jumpsuit for the ceremony.
OP here,
That's really pretty. It's also too much for what I want. Too much cleavage, too much . . . I don't know how to describe it.
But I want sleeves because I want sleeves. Not because I believe I need sleeves to be in church or whatever, but because my preference is for clothing with sleeves. I think I look better in sleeves. So, getting something that's clearly designed to be worn without a cardigan, and adding a cardigan for church, reception, photos etc . . . seems odd. I can see getting a sleeveless dress that looks really good with a jacket or a dressy cardigan, but to me this isn't designed for that.
Also, I want a dress. I've worn some variation of pants to lots of events in the past year, including events where most other women would have worn dresses. I wore pants to my kid's first communion, and another family wedding that was much more formal than this. This time, I want to change things up an wear a dress.