No, I don't want to talk about Lycra shorts, although I've thought about that.
Instead, I'm thinking about long sleeve, thermal jerseys-- the kind cyclists wear in winter. Seems to me that a jersey designed to be light in weight and wind-resistant might be a reasonable choice for hikers-- it would keep you out of the cold, pack down small, and plus, it would work well as a second layer under a shell jacket or to sleep in, since it would fit relatively tight.
What do you all think? I'm just curious, since I'm a cyclist who has a bunch of jerseys in his closet, and I'm trying to finalize gear plans for a thru-hike next year.