Hi Dikki
I get you now.
With OAS 7 you can do what you require with the instruments, styles etc, (They all have 2 reverb settings each, thus allowing one to be assigned to presets and the other global) however as far as I am aware the microphone, and any other equipment that is connected has to be adjusted independently. (OAS 7 users will probably be better to answer this as I am still running OAS 6)
Hope this helps

Bill