It would have focused on conflict between ”religious fanaticism and unbounded science”, which the award-winning BioShock does touch on.
We would have played as Carlos Cuello, sent to Isla de Salvacion in what appears to be modern times as it meantions ”MP3 Log Files”. We were there to ”infiltrate a religious cult on a remote island and ‘rescue’ a wealthy heiress from the clutches of the cultists”.
Instead of battles between Rapture looters and the belief of rational self-interest though, the original would have tapped into ”the terrifying nexus between religious fanaticism and unbounded science”.
It would feature plasimids still but certain ones would also alter the appearance of the main character, with players able to witness the changes. A lot of the original concept did in some way translate over to BioShock, except the environmental hacking like messing with oxygen levels or upping humidity to give yourself cover through fog.
An interesting 9 page read on what could have been - thank you Irrational Games.
Source: Eurogamer