Well I have been thinking about the Hematophage Perk, and I thought that after we have it maybe blood packs could not only heal more but also reduce the hunger and thirst of the LW (maybe just a little bit since it is rad free, like 10 or 15 on each), because the perk is symbolizing how the LW now can get nourishment from blood packs (which I think might include food and drink since The Family only food is blood and they don't seem to need anything else).
Also maybe in some conversation options that check for the Cannibal perk or a speech check we could reduce that check if we have the Hematophage Perk and not the Cannibal one. For example the Our Little Secret unmarked quest or the Beyond the Beef NV quest (which requires a 62 speech check, maybe we could reduce it to 50 or some other value), after all we do feed on humans too but just the blood.
Just my thought on this perk.