if you ONLY need it for collisions, just look at the connections from the nRigid to the solver and make those connections to the other solver.
connectAttr -f pPlane1_nRigidNode.startState nucleus2.inputPassiveStart;
connectAttr -f pPlane1_nRigidNode.currentState nucleus2.inputPassive;
if you are planning on doing any constraint to the nRigid DONT do this, duplicate the objects as mentioned above
oh, and as with most node hacks on nCloth nodes, you will likely need to force a refresh, ie rewind timeslider