Multi-track effect processing with AudioSources?

My application currently uses a MixerAudioSource to mix several AudioSource together.
Now I would like to apply one or more chain of plug-ins (for example PluginGraph in AudioPluginHost example) to various subsets of the audio sources (which is similar to what we would do in a DAW).
Some questions about the best way to do that:

  • Would I have to rewrite the AudioSource so that they are processors instead?
  • Shall I share among the app a custom AudioBuffer with one channel per pluginGraph?
  • Is a thing like megamixing multiple MixerAudioSource imaginable?