Ok, ill see if can help explain it.
Every part of the minifig is a "Node"
Nodes are like Lhand, Rfoot, Skis, etc.
When you select the Node on the avatar options menu, you "Un-Hide" the node.
For example, Download the bot mod and spawn a standard bot.
Then, on the veichle spawn, put this into the events;
OnBotSpawn>Bot>EditAppearance>UnHideNode>ALL>(Make the color box white)
Then respawn the bot. you can see that it unhides all the nodes on the bot.
In order to make more hats,, you would need to edit the whole minifig.