These are just things that I'd plan out, so ideas that hopefully help!~
is the pattern I use for under-bust corsets, and it rocks
You would have to modify for the front lacing, but it shouldn't be too hard.
As for the boots, I'd find a base pair and build on top of them. I'd lean toward a combination of wonderflex, EVA foam and craft foam with plastidip. As for the raised details, puffy paint and some black paint weathering is your friend. Same deal with the gloves, necklace and tiara.
As for the "ring of doom" I'd try out layered wonderflex with foam first, since it's pretty lightweight and sturdy. Have it attach at the front via industrial grade velcro. Then I'm thinking of some kind of harness in the back, similar to the fairy wings at Disneyland or this seller
. It includes two poles that slide into boning channels--maybe use some clear acrylic like a wand from a venetian blind so that's even less noticeable
It would make the ring closer to you in an oval shape instead of a circle, but would be sturdier.