I've been thinking about this as well. The way I interpret the current firmware you can exclude the power amp and the cab from a preset sound (regardless of where you have placed the amp and cab block in your preset) by using the Global Settings according to below picture. My conclusion is that even if a preset have an amp och cab block these are removed from the final signal coming from OUT 1 and (depending on global setting) OUT 2.
View attachment 50580
My suggestion is to move these settings from the Global Settings menu to the I/O Settings menu. In the I/O menu you can set a few things separately for OUT 1 and OUT 2. The AUDIO page of the I/O menu contains parameters that affect audio routing.
Today the menu looks like this:
OUT 1 (MAIN) MODE
OUT 1 (MAIN) PHASE
IN 2 (FX RTN) MODE
OUT 2 (FX SEND) MODE
OUT 2 (FX SEND) PHASE
OUT 2 (FX SEND) ECHO
I suggest that it looks like this:
OUT 1 (MAIN) MODE
OUT 1 (MAIN) PHASE
OUT 1 POWER AMP MODELLING (ON/OFF)
OUT 1 CAB MODELING (ON/OFF)
IN 2 (FX RTN) MODE
OUT 2 (FX SEND) MODE
OUT 2 (FX SEND) PHASE
OUT 2 POWER AMP MODELLING (ON/OFF)
OUT 2 CAB MODELING (ON/OFF)
OUT 2 (FX SEND) ECHO
...