Suggestion about fixing the mutagen system
The mutagen "bullet time" effect needs tweaking. Most of the time with the current system, one of two things happens:
1. You find a barrel of mutagen, load up on it in case there are some bad guys round the next corner. You spend half a minute walking along a corridor in slow motion, and by the time you find some enemies, the mutagen has worn off.
2. You break a barrel in combat to try and take advantage of it. However, by the time you've managed to stand in the cloud for a couple of seconds, either you're dead, or your enemies are.
I suggest a system where the "bullet-time" effect from mutagen is inactive, unless the player is "in combat" (by whatever definition the game stats already track) or fires a weapon. This solves the problem of slow-motion corridor walks.
When not in combat, Blade's mutagen level would still decline, but much more slowly. This would stop the player using mutagen in levels where it's not intended, and give some incentive to get into combat hastily.
It also means that the "bullet-time" effect will tend to last for the beginning of a combat - just long enough to give the player a chance of surviving an unexpected attack.
The typical experience with the modified system would be:
1. You charge up on mutagen and bust into a room, but it's empty. You move on to the next room, and your mutagen bar is still half full when two Syntex goons drop through the skylight. Instantly, slow-mo kicks in and you have enough time to headshot one and take cover before the next one can shoot back.
2. You break a barrel in combat and run through it - since you are in combat, the effect kicks in instantly.