This is a long shot, but is there a way to specify elements which should be excluded from a given load case? For example, if I have a rigid link cluster which connects to four bolt points, but then under certain conditions only connects to 3 of the 4, could I define two RBE2 elements, and specify that only one is active, then the other, depending on load case?
Two possibilities I can think of which use the entire model.
One is to use MPC equations instead of RBE2, if nodes are coincident, writing the MPC is easy, and you can change MPC sets between subcases. This means you choose the load path for each subcase by picking the desired MPC's to be active.
The other option, if the load path is "directional" you could use gap elements so they are only active when load is in the the desired direction.
Another option is to use groups to create "different models" within the modfem, then run each load case individually and write only the desired group for each loading.