I've used a white polypaint diffuse bake to help with an alpha before, though the object was harder than hair. You'll probably want better sampling, and depending on the result you may need some light photoshop work (I'm not sure what the correct term would be, 'feather' maybe?).
Thank you again for the response, Pior! I'm a big fan of your work. Very inspiring. :) I actually gave it a shot last night--painted the highpoly white and baked it to be used as an alpha. Baking it to the polystrip worked fine--I just made sure to run the ray tool in xnormal to get the correct ranges and it baked pretty…