How the Base Package Models are decided?

Hello,

I am interested to know about the thought process/decision how the base package models are decided?

Is it based on popularity of the real model or Technical aspects to model or something else ?

I believe the success of the real world models have an influence on models the simmers want to fly.

For Ex : Many may prefer flying say 737 -800/-700 over the -900/-600 models of B737 just because they are hugely popular over the

latter models. But PMDG modeled -800/900 into one and -600/700 in another as extension. This made the -700 if someone wanted to be 
a very costly product and end up owning -600/900 which one many not be specifically interested in.
 

If we go by the Legacy of 747, -400 was released and later -8 and LCF models which sinks up with the real world numbers.

With B777,
going by numbers B777-200ER is the most popular of the -200 Series with about 422 in number.
So I had predicted this as the Base model and -200. The "A Type" (88 Built ) and LR (~56 Built) probably would have been made available as Extension Type. But PMDG chose to have the LR as base package over the other popular series.

Many would probably want -300ER model to be flown over the -300 Series again only because of ER's popularity in real world.

Kindly share what goes-in while deciding the Base package types (Of course, only if it can be shared. I understand and respect
if PMDG wants to keep it confidential).

Best Rgds
Cheeleair.

(NGX,MD11,-400X,777LR/F)