The sleeves are next, and I'm not sure how to proceed. The real solution is that I shouldn't have been so impatient six months ago to get to the arm holes and have made the shoulders much, much wider, but that's not very helpful now.
Here are my two options: On the left, do some crazy impromptu picking up of stitches (and be VERY careful to do it evenly!) and fill in the open triangle-y area, then make up a set-in sleeve pattern. On the right, extend the sleeve cap like it should have been in the first place (lesson: LEARNED) and pick up the underarm stitches and continue it raglan-style. Knitters, any advice?
(Here's the project on Ravelry.)