Well as long as the catsuit would have an opening in a very destinct area between the legs I might think of one kind of use for keys ... wow, suddenly "Houston, we have a lock on the G-spot" has another and not that much different meaning On the other hand the suit might be so think that it doesn't need any restraints, it would simply restrain the wearer by becomming extremely clumsy. Of course at such a thickness all features of the wearer's body get lost. But on the bright side: At a certain thickness you can add locks ... like it's popularly done with doors and chests ^^