I don't think you want boning on the bust - I think you want to shape the seams in-between the "petals" to keep everything flat against the skin and accommodate the bust - think of them like darts or princess seams - something where you can adjust the fit.
Making it a light corset is a good idea, but I would use light boning unless you want more and I'd make it so you can't see the boning from the outside so you get a clean look - have the boning on an inner layer for support only.
I think this is a good costume to talk about how to view these things. I wouldn't look at them as a combination of garments. Look at them as 3D shapes and places with potential to fit and drape. That way you're not trying to cobble things together and force them to work but just taking a body-shape and dividing it and adding to it.
If my friend was doing this I would start out by drawing a body block and then go from that - just drawing the seams on to it and adjusting it. It's a good skill to learn if you think you'll do a lot of costumes. I'm making all the patterns for my friends' costumes - once you know how to do it you can apply it to anyone and anything !
You might also check out this thread : http://www.cosplay.com/showthread.php?t=320695
and sign up to be one of the test subjects for the custom patterns.