Of course a 'bend torso forward' dial can (should?) have a 'hip back' component to maintain equilibrium around body X axis. Same for 'hip side' to keep Z-axis equilibrium. For arms off-from-horizontal and off-from-sideways same, but to lighter extent, could be done. In the end it all adds up in a linear way. 

There is some margin because out feet have a support area larger than zero. In view of that the above may be sufficient. Weight of things held in hands plays a key role but  cannot be automatically accounted for. Weight is not a parameter in the Poserverse. To cater for that a general 'hip side-to-side' and 'hip forward-aft' could be useful. 

Poser figures have actors for 'centre of gravity' and 'centre of area'. I have never used them, not sure how good they are.