With a lot of the animations I've seen between two characters, or a character and an object, the poses seem "floaty"... What I'm looking for is a "Constraint" and the ability to lock-down a limb to that constraint (I suppose with a distance/force "release" option). In production 3D packages, a constraint can be placed anywhere (often on the edge or surface of the surface of the object) and can effect another object regardless of the other object's animation...
Let's say one character has constraints on their hips (character 1), this doesn't effect the movement of the constraint-bearing character (character 1)... the other character (character 2) could dance with the first character (character 1) and hold character 1's hips (have character 2's hands anchored on character 1's hips) while moving in the general proximity.
I am used to animating constraints on the surface of objects... perhaps this could be solved in Poser (ug, so simplistic) with some scripting help.
DT