Since raising dragons will be an important aspect of this, some suggestions for raising dragons.
Grooming, either with sheers or a mod original item, players could groom their dragon to keep up their affection, (you know in case they accidentally hit it). You could get scales from it, or not if it's not shares, but say a brush.
A special item that let's the player see their dragon's stats, like health, hunger, if they are in need of grooming, time until the next stage, affection level, maybe even mood. It would all help make the dragon's feel more alive and less like stereotypical minecraft pets.
An item to call your dragon, in case the player and their dragon get separated. Each item would be bound to only one dragon, or a special version for all of them.
Dragon related weapons: I know there are dragon based weapons in planning like the bow, but there could also be such things as dragon bone swords, armor (if it isn't planned already). Also an enchantment called Dragon's Bane, which is used by enchanting a sword, or other weapon and using dragon's blood (the story that only a sword bathed in dragon's blood could slay a dragon). It, obviously, would do extra damage to specifically dragons