Angelina so would you say that it is almost impossible to design a corset that is as secure as a chastity belt but does not restrict movement more than a belt? how would you compare this to thighbands?
That depends on the purpose of the corset! I mean the whole point of a corset is support (or severe restriction in some cases). So a metal corset is going to limit movement completely and make normal life very difficult. As @youdontknowme mentioned, the spine moves a lot more than people realise. Something like a waist cincher could work. But even then, walking would hurt eventually as each hip bone lifts, and this would be rubbing on solid metal.
At the other end of the scale, there are plenty of fabric corsets that don't do much at all. I imagine the one Avery posted earlier wouldn't restrict movement in the slightest.
It's easy to design a lockable corset too. You can put a lockable flap over the laces... A similar system is used in a lot of strict fetish corsets, posture collars, catsuits and so on.
I think someone like HW Design in Austria would be able to come up with something that incorporates a slimline crotch shield on their system corset. WARNING: fetish content: https://www.hwdesignshop.com/lng/en/corset-13-combination-corset-cor-13.html
Trust me, if you're laced into a system corset and posture collar by someone else, you are not getting out of it on your own!
Regarding thigh bands... Not sure we can compare them to corsets as they have a completely different role. It's possible to make all three inescapable, so clearly the best option is corset + chastity belt + thigh bands! π