for the first question:
you can create a virtual sequence class which contains the handles of real sequences and sequencers.In the pre_body method just create the objects for the sequence handles,and in the body method start the particular sequence using the particualr sequencer handle.
in the class test create the objects for virtual sequence handle,and in the run_phase assign the real sequencer handles to the sequencer handles in the virtual sequence and start the virtual sequence using start method.