I suggest for the Strength bar’s functionality to be re-added into the game, as the Hunger bar was recently added back not too long ago. The strength bar used to work pre-shutdown where I believe max strength would mean higher punching damage, but this could also be expanded upon.
You would increase it by using the treadmills or weights in the back room of the CD cell block or at the Phi gym, or by punching other people.
For every portion of the strength bar you fill you would get higher punching damage and maybe gain some extra resistance to melee weapons, or maybe even firearms meaning you would take less damage,
At 100% strength, you gain the ability to carry 2 SCP boxes at once for faster SCP transportation.
The strength gained would not be permanent however and would have to be maintained by working out.
A gym could also be added to MTF and SD spawns too so that combatives can increase their strength bar.
The resistance to firearm damage is probably a bad idea, so I’d say keep it to resistance to melee weapons / punches only.
The animation for carrying 2 boxes would probably be more like holding 1 box in each hand as your character is stronger and can carry a box with just one hand, and perhaps it could be restricted to 1 large box & 1 small box, or 2 small boxes.
As for the combative gyms, regulations could be added to restrict combatives from working out in the gym for longer than 10 minutes at a time, to prevent them from neglecting duties while still allowing them to have some time to build their strength bar, additionally, they could just go onto the FP team and use the Phi gym instead.
The animation for holding 2 boxes doesn’t need to look great, and if it really does look that bad when you’re holding 1 box in each hand the boxes can just be stacked on top of each other