For the additional 2 channel setup, I did this for my own house.

SB doesn't like if you remove pages, but you can add pages (in VTpro) without breaking anything.

To add a separate stereo set to my system, I added a new room to SB, put all 2 channel equipment in there. Add an dummy PTX3 to the new room to generate pages for it so you can later copy-paste them to the real interface.

Open the real interface, add a page for the 2 channel amp (e.g. by copy paste an existing one) in the same room and add some buttons for input / volume etc.

Add a button to the systems home page (call it 'listen to stereo' or so, I removed the climate icon to make room for it) and make it flip to the new amp page. If you wish you can let it switch the power on to the 2 channel set or you can provide separate power buttons on the touch screen for them (some people they want to keep power always on, claim better sound).

If the customer is never going to use the climate section, you could consider to edit the project's defaults to use the 'climate' hard button to flip to the 2 channel pages and change the 'climate' text to 'CD' or so.

When finished, don't forget to remove the dummy PTX3 from the project, otherwise the project will not upload properly.

It's a bit much work I have to agree...