I have created, in PnP play, swords named "FrostFire" (longsword) and "Freezerburn" (shortsword). They had icy blue flames when "ignited" and did both types of damage. A bow with these properties seems magically possible. It is like the old Dragon Magazine argument- "You can let yourself believe in Dragons, Mages and Elves, but you say that chainmail pant's are impossible?" I love the capabilities of magic!