pretty wet here in Porltand OR. I find it manageable to keep down dry.
I use a 2.5 oz Apex vest for survival reasons – if all my down gets wet, maybe the vest, jacket, and other stuff will keep me alive. An Apex quilt would be a lot better than down if it got wet.
I use asymmetric sewn through baffles – the ease of sewn through baffles with the performance of regular baffles. Inner fabric has, for example, 2 inch wide baffles, outer fabric is 3.25 inches. You can scale both up for wider baffles.
1 foot square test piece:

side view:

Theoretically, cold air can get between the baffles, but if there’s a fabric layer on the outside it will be a dead air space so doesn’t matter. Even without an outside fabric layer there’s a skin of dead air above the outside surface so it doesn’t matter. If it was windy maybe it would be worse.
You also have to make the outside fabric 0.625 inch wider in the other direction. And sewing it together is weird, you have to do some folds to get the fabric to line up. Make a test piece, like this 1 foot square to get the technique down.
This is a far out idea. I’ve made a couple quilts and a couple vests successfully. I don’t think I’ve convinced anyone else to try it though : )
Another advantage is there are no hidden seams. If a seam starts to rip out, I can just re-sew. With regular baffles one side of the seam is hidden inside, difficult to repair it.