[Help] How to do necklines that plunge to belly button? Sewing Machines Parts and Sales in Los Angeles

I’m trying to make a dress with a neckline similar to Nicki Manaj’s 2010 VMA dress

NSFW because neckline plunges to belly button:

http://imgur.com/3HtvFD8

Do you guys have any tips on making something with this deep of a neckline? I may just be overthinking it, but I’m seriously not understanding what I need to do to make something like this.

Nicki doesn’t have any clear straps holding the two sides together. I know that fashion tape is being used, but can’t help thinking that there is more to it.

Are there built in cups? Without a middle area, would that even do anything?

Do you know any patterns/tutorials for something like this?

In case you’re wondering, it’s for a cosplay.
http://imgur.com/8Ff83c4

Thank you!