Toss the jacket concept, think systems. Until temps get below freezing I don't see any advantage to lofted gear, regardless of synthetic or down. You end up with one light but monolithic garment that really can't be used for anything else. Fleece is heavier but much more versatile and superior in wet conditions. You can always get lighter, but at the cost of functionality and sliding over to the stupid light column. At some point, you have to bite the bullet on clothing weight, but that doesn't mean giving up on a coordinated system that is warm and breathable and can be worn in many combinations.
I don't see the point in the existing SUL rain shells-- too expensive, too fragile, typically weak on venting options and a trim fit making them less breathable and giving less coverage. Rain gear needs really vary by region and climate. You can get away with some very minimal stuff in dryer areas where you might deal with an occasional shower. It becomes radically different when considering wearing a rain shell all day or several days in a row.
Rain gear options:
Poncho (rain gear, pack cover AND emergency shelter) 7oz or less
DriDucks, weights vary with type. 6-12oz?
2.5 layer rain shells, 12-16oz
Windshirt, 4oz or less
Fleecy mid-layers: Patagonia R1 or Power Stretch, 10-14oz, or vests in the 8-10oz range
Base layers: silkweight on up to Cap 3, 5-10oz