i read ur posts. the gsc have a lot to learn from u - nice thoughts. in my opinion, in stalker2 u could select 1 character from few in the beggining of the game, every character would change the storyline a bit. every character would have his abilities, features.
i think there should be more options in converations when going on quests. there was options in cop but only in few quests. these options in conversations would change the ending of quests, rewards or even the storylines ending a bit.
There could be awesome to add possibility of moving some props, then stacking and gluing one to another. So you can build your own hideout from garbage laying everywhere.
Also please take a look on modifications popular to this date: garry's mod and san andreas multiplayer. Players can there exploit game content and in result they code thundreds of unique gameplay servers. If STALKER 2 will allow more than 32 players to join the server, then you will get chance to gain popularity of the game.