I got in touch with this amazing guy who works with latex. The long and short of it is that I'm going to be pestering this guy for help with every latex related problem I have.
He has a couple of good tutorials on making latex body art like horns and spines etc. and a really good tutorial on a wig that would be perfect for Kerrigan.
Here's the links for anybody attempting something similar.
The way I think I'll do it is carfully constructed pannels of latex. Outer upper leg, inner upper leg, front knee, back knee, lower back leg, lower front leg etc. each of these will have any needed spines and textures and horns attached to them, with seams in conveniant design lines, like under a long fold, or at parts of my body that will flex and show lines anyway.
In this way, my whole body will be covered, except for my hands and face, however these will be painted to blend seamlessly with the latex.
The latex parts will be made by painting a few layers of latex onto greaseproof paper, and sticking cotton wool wadding, mountboard, craft foam etc into it and covering in more latex to keep the weight down on each part. Have a look at the tutorials done by Marshon, they show the prossess in detail.
Finaly, the paint will be applyed and varnished in place to give it a slimy shiny look, the parts that join onto my bare skin around the face and wrists will have plenty of room for face paints to be blended. That way I can clean off most of the face paint between uses and keep her good.
One of the problems with latex is that it likes to stick to it's self. After making each part on the paper I'll be brushing it with talc to stop this, but the part that connects with the skin will be kept clean to help it stick to my skin... so each part will have to be stored on paper, flat and protected by individual boxes for storage and transport. Not only will I need to to tests to see if this will work, but at the best case senario this will be the bulkiest cosplay I've ever thought about doing...