Make ghasts only attack players that aren't at max health

With the upcoming ghastlings, it's hinted that the ghast isn't native to the nether since they need water to survive. Plus, ghast tears are used for brewing regeneration potions. I don't think making ghasts hostile on purpose fits into their character as (former, at least) parents/guardians/healers of the ghastlings. So, to still maintain their hostility while having it fit with the mob, I think the ghast should only attack players who aren't at max health in an attempt to "heal" the player from their perspective- like they didn't originally shoot fireballs but rather something healing, but they were corrupted by their stay in the nether.