I have a lot of time to think about this so it's mostly a thinking point for me.

I have a wedding to attend (as a guest only, not in the party) in July of 2019 and I've been asked by the bride to wear my kilt. I don't yet know what time of day the wedding will be. I have evening jacket covered with the BBSBA but if it's a daytime wedding, I'll need something to wear over my shirt and tie that's less formal. Ideally, a light tweed jacket.

However, I don't have one of those and they're pretty expensive. Given my recent profound lack of success in converting a regular tweed jacket into a kilt-length one, that's not a realistic option either. What I do have are sweater vests (dark and light) and cardigan sweaters (again, dark and light).

How appropriate would either of those be for a daytime wedding in the 'states? I wouldn't button the cardigan if I did wear one. I never button them.