I've seen more than a few first-time SS2 players pick OSA because of course psi powers are like so totally cool man, and subsequently have a terrible time. I wonder if it would be overkill to, when players approach the OSA tunnel, pop up an onscreen message something like "Warning, not recommended for inexperienced players."
Maybe even expand this to a popup for every service, since this area can be frustratingly cryptic for first-time players. Like if you approach the Navy tunnel, you'd get something like "Enlist in the Navy for a career focused on technical skills." Marines would get "Enlist in the Marines for a career focused on weapons." or whatever. Sure this sort of thing seems obvious to us, but at this point the game hasn't straight up said it, and character creation is the last place you want to be coy with the player.
I feel like the 3 preceeding training booths already explain in detail what each branch of service does, and having messages pop up in the middle of these hallways seems like it would be very intrusive.
If you REALLY want to do this, you can make it more immersive by putting one of the tutorial computers on the wall in the hallway leading to the career selection, with text like:
"Here, you will need to select a branch of service. This choice is permanent and cannot be undone.
Your branch of service will determine what choices you are offered over the next 4 years, however anyone is free to pursue any skills they wish once training is complete.
The Marines are focused on weapon skills, the Navy are focused on Technical skills, and the OSA is focused on psionics.
OSA is not recommended for first time players!"