Hi,You have to buy the PMDG 747-400X first, that's the base package then you can buy add ons first, notice on each expansion pack there is a notice in red saying that you have to own the PMDG 747-400X before getting this add on or expansion pack.
Actually I fly mostly in the United States because charts are easy to access online and there are alot of airports suitable to land a 747 around when you're flying and a problem happens, I don't usually program any failures in my flight until I know everything within the aircraft
The Boeing 777 doesn't have analog standby gauges and it's working perfectly fine, in my personal preferences, I would like to be able to choose which one I want in the cockpit
I don't think it really should be a separate product because it will require lots of effort in developing an exact flight model and systems modelling for the 747-8
PMDG just created an exterior model of the 747-8 and didn't focus on any flight characteristics or anything like that and everything is just like the 747-400, it's just an exterior model, I bet that's why you are seeing in your FMC ident page aircraft type as 747-400
In most payware aircrafts, there isn't a feature to share the cockpit unless someone comes up with a solution to be able to share the FMC also then sharing a cockpit in a payware would work