While I'm sure people would just brush it off as gimmicks, I'm mainly looking at it as various objectives within a fight other than just taking a mob's HP to zero.While i agree, I must ask. What does pose a challenge to you?
Let's say there's a really, really, really effin' big Ironclad mob, like one foot is the size of a tower. Players could technically enter the inside of the mob, but would possibly face environmental hazards like electrical currents or moving pistons on top of possible internal security mechanisms. Now, you'd want a small party on the outside to be keeping this NM busy since it'd otherwise be able to focus more on ousting intruders. Those on the inside, however, could seek out its power source, whatever "brain" it has, and other possible objectives with the interior itself being randomized enough that every fight can be new enough.
None of this should require an exceptionally rigid party structure like CoP did, but just something sensibly balanced like a tank, healer, a couple DDs, then some support.
As much as some people have creamed their pants over CoP's airship fights, I actually felt they were pretty lame. We had no "feeling" like were in air, but instead it was just your usual stationary battlefield with a pretty background. Now, what if you introduced turbulence, or a means to knock the mob off and win more easily? Protect the engines? Fend off other airborne attackers? Use your imagination.
In a nutshell, I'm seeking more complex fights, not necessarily more difficult.