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!
Burgundy Red Lattice Front Halter Bikini Suits features criss cross lattice design,and structured bust cups. Fully lined, back S-hook closure. Perfect with red Bottoms, or mixed up with anything you're feeling.