Personally I am a fan of that idea:
ally must have free reaction with which he can catch the potion and drink it
combined with a dexterity check of the catching ally. If the ally is prone or dead only a natural 20 will work. As a DM I would explain a natural 20 like: "And the potion opens itself while flying and the fluid drops exactly in the opened mouth of the incapacitated ally."
It definetely makes more sense than throwing a potion against the head of my dead companion to revive him.
