In keeping with bulking up your "Day" pack, consider what happens when you really need it to be an overnight pack because things went south. Maybe it's not so bad that you need to activate your PLB, but something in addition to your mid-hike snack may be in order. A small Ti (Snow Peak 700) or stainless pot that can boil water, soup...whatever may be a good addition -- instant soup (chicken noodle?) & tea come to mind. Other than an overnight, standard EDC items should be more than adequate.

(I prefer nalgene or other polycarb bottles to bladders for carrying water. Just a preference.)