ok - I do not know, so these are my guesses...
corns do not naturally live where cactii live, and so it would not be naturalistic in the strict sense for them
I know if I am near a cactus I will get stuck on it no matter how much I try to avoid it. I am going to assume for the point of this post that snakes are more adept than me, and once they know what it is they will avoid it from then on. However, since a cage is a small contained environment, all I would think you are doing is limiting the size of the cage they can utilize. Therefore I would guess - no - don't use one.
I welcome other opinions on this.
Skye