lol I had the same idea about adding a nether star chicken.

My idea was to make it so you had to craft it with 3 wither skulls and a nether star, basically kill the wither first as to not mess up progression.

Yeah, that sounds great ;). I would like to make it challenging as well.

Maybe make it so it drops a star only a couple times a day?

You could make it drop nether star nuggets. Combine to make a star.