Suggestions

This is cool feature that phantom will help mob to reach player, but if he flying they just standing on the ground. If they will chase player when player higher in air than them it would be fantastic!
Also skeletons cant use axes and swords if they have it.

Solution

I think tracking Y player pos will do this with ease
for skeletons - maybe some changing arms when skeleton have melee
For tacz - maybe tacz npcs mod will help if you want to do it