This is a great idea--to add crochet motifs to an existing bra. I would leave the original cup in, because then you would end up with a crochet bathing suit top that wouldn't stretch and fall off when you wore it into the water!
Did you know that no two people have the exact same eye color? Did you know that every person who has blue eyes comes from the same ancestor? Take a look at this info-graphic which reveals some interesting facts about eye color.