Restore for bike packing doable?

I have had this old Gottfried bike laying in my garage for a while. I think it's a pretty cool bike.

Before starting restoring it for bike packing I'd like you opinion on this :

Can I swap the rear cassette for a bigger one ? If yes, do I need to change the derailleur as well?
Or the front for a smaller one ?
Or both ? 🙂

If yes, which part should I look for?

I live in the alps, so there are plenty of steep heels/climbs.

Also, if anyone has experience bike packging with such a bike what do you think of it?

Thank you and have a great day!