Sure thing.
Did we start writing up Swallow Whole anywhere for this thing?
Let's try this as a draft:
Swallow Whole (Ex): A draeden can try to swallow a grabbed opponent which fits in its Engulfing Maw by making a successful grapple check. Once inside, the opponent takes 10d10+45 points of crushing damage plus 8d12 points of acid damage and travels X ft toward the draeden's central body. A swallowed creature can cut its way out by using a light slashing or piercing weapon to deal XX points of damage to the interior of the tube (AC X). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out. No creature with speed less than XX can climb out of the draeden's maw by making an opposed grapple check. A draeden can hold an effectively limitless number of creatures up to Colossal size.
Ummm, "very big"?I guess the size penalty should be whopping, but it's kind of limited by the rules, since they're not really designed to deal with something this big. However, NA should be tremendous. The converted AC is 40, but that vaguely feels a little too low. Any thoughts?
So the throat/gizzard is AC 25? Might be too easy to cut out, do you think? Well, I could go with what you propose or even boost natural another 10 points.
Hmmm, I can see the divine bonus, but I don't see how its Wisdom will allow it to prepare for and avoid attacks from inside itself. So how about we add divine but not insight.