A good option might be a jacket with removable sleeves that can be worn as a jacket, vest, or just sleeves. Plenty of times I've hiked with my back covered by my pack and really just wanted something on my arms.
For this I can use a fleece sleeve/shrug and add a tunic when I wish. This fleece tunic has a neck zipper and can be slung below my hammock for bottom insulation. The system is a bit bulky but cheap and effective.