Are the penguins breedable? If not, they should be! Maybe with raw fish as their item

Also they should drop feathers/eggs like chickens do :D so we can have penguin farms instead of chicken farms

Yeah that would be amazing :D

The penguins are already breedable with raw fish or raw salmon.
There is a config option for penguins to drop fish. If you wish them to drop something else you can also turn on that config option and then change with a resourcepack what you want them to drop.