1.Allow mobs to help you out in fights against mobs and players. In order to get the pets to attack players/mobs you could either have an auto attack system or by using a command.

Here are some example commands:
/pet attack (Nameofplayer)
/Pet attack (Attack everything that comes near it)

Might be helpful to have worldguard pvp flag support.

Fix the flight height of the enderdragon (Currently goes into the ground)

Don't know if this is possible but anyway here is the idea.

Allow you to pick up other players on the enderdragon so you could have a couple of passengers which would be helpful for clans.

Commands:

/pet addplayer (Nameofplayer)

This is so you can players as passengers to your pet

Thanks for your time