Paul Davis:
  so when a user decides to insert a plugin that has 2
inserts and 2
 outputs in between 2 plugins that have 1 output and 1 input
 respectively, what do you propose to do with the signal?
 when a user adds a 1 input plugin after a plugin with 2 outputs,
 what do you propose to do with the signal?
 when a user deletes a 1 in/1out plugin from between a 1out and a
 2in plugin, what do you propose do with the signal? 
I must be missing something because the answer seems so simple:
Clone / mixdown on all of these occasions? Plus a walk through
affected regions of the plugin chain to reconnect?
Wolfgang