Not sure if I understand what you're saying. You can already reverse audio and MIDI in arrangement view and edit envelopes of clips in session view in live 8.
And what do you mean by gain processing and printing device processing?
in arrangement view you can't process audio, as far as gain , reversing, etc. thats all done in the session view then recorded into arrangement.
but it would be nice to have options to do some processing tasks in arrangement view.
in session view it would be great if we can cut audio within clips.