Here's some links to some beta content for both Blue Shift and Opposing Force. Some of it is really interesting such as the barnacle gun sticking to multiple surface types and the Pit Drones being slaves to the Shock Troopers. As well as cut audio that gives extra context to things. Some of this might be worth considering to restore in the remake or not.
(Beta content from trailers and pictures of opfor)
youtube.com/watch?v=rSyZNGQtuo0
(unused audio)
youtube.com/watch?v=o0I8frE8w_4
(unused model animation)
youtube.com/watch?v=LE94dCsxFEw
(TCRF wiki on opfor)
tcrf.net/Half-Life:_Opposing_Force
(unused intro animation for dreamcast blue shift)
youtube.com/watch?v=lFlEj8JvvqU
(TCRF wiki for blue shift)
tcrf.net/Half-Life:_Blue_Shift_(Windows)
(Beta content from trailers and pictures of opfor)
youtube.com/watch?v=rSyZNGQtuo0
(unused audio)
youtube.com/watch?v=o0I8frE8w_4
(unused model animation)
youtube.com/watch?v=LE94dCsxFEw
(TCRF wiki on opfor)
tcrf.net/Half-Life:_Opposing_Force
(unused intro animation for dreamcast blue shift)
youtube.com/watch?v=lFlEj8JvvqU
(TCRF wiki for blue shift)
tcrf.net/Half-Life:_Blue_Shift_(Windows)