Spawn Mobs Safely

I want to reduce the trouble of getting rare animals like mooshrooms, polar bears, skeleton horses, etc. I am going to make a plugin addon to slimefun where you can spawn in a mob with a command, when you have a certain item in your inventory. That way it may take a bit of a grind to get the mob spawning item, but it will be better worth it than spending your time to go and grab one off another biome thousands of blocks away. Message me what you would think about this plugin.