After finally getting a chance to see where I left off with my project to fix version 1.2.5, I most likely left off at porting client-side implementations to the server code.
One of the biggest hurdles is to figure out how I need to change or implement new packet classes to handle the extra data tied to things.
Packets are strict and have to know the size of the data being sent, so I can't just add extra informaiton to an existing packet without also adjusting the defined size in bytes. Prior to my changes, all mobs had very simple data to send to the client, like entity ID, mob type, x,y,z position, pitch, yaw, rotating(boolean), head yaw.
Very simple stuff, but with making zombies lose their heads and rise from the ground when they spawn and giving animals a sex type, and all this other stuff it makes everything now more complicated, and will probably mean I need to implement my own packets for this.