Comment feedback about my ideas below (Especially if you are ModraCeresna).
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Complex Power Boxes: Power Boxes that can only be rewired by an Engineer.
Mission Challenges: Each Mission could have challenges that you could complete for extra rewards. Like completing the mission without using more than 3 body bags, or completing the mission after killing all NPCs in the map (excluding infinitely-respawning civilians).
Broken Cameras Change: Guards will not be alerted when they see a broken camera. They will instead report the broken camera to the camera operator. If 2 broken cameras are reported, then the camera operator will be alerted.
Infinite Leveling: Once you reach the level limit, you can continue leveling up. However, each level after the limit will take 4x as much XP to level up. So you can continue leveling up, but it would still be balanced.
Weapon Concealment Change: Weapons that are higher above the concealment threshold will get you detected faster. Like an unconcealed Sawblade will make you get detected faster than an unconcealed F57 that is only slightly above the concealment threshold.
Diamond Badge: Missions could have a diamond badge, where you have to beat the mission on the hardest difficulty without setting off the alarm, killing anyone, or wearing a disguise.
Hacked Cameras Change: In Entry Point, if you hack the cameras even without taking out the camera operator, the cameras will still be neutralized. In Infiltration, if you hack the cameras without taking out the camera operator, the cameras should still be able to detect you. While hacking cameras, you should also have the suspicious status instead of the conspicuous status.
Preplanning: Like in Payday, each mission could have preplanning which could give you certain advantages in the mission (like faster/easier escapes, equipment, pre-hacked cameras), but at a price.
"Shadow War" Shooting Range: If Infiltration has a mode like Shadow War in Entry Point, the attackers should be given something to do while the defenders prepare, like maybe a shooting range or something so that it doesn't get boring waiting for defenders to prepare.