From the gameplay video (E3) Jason picks up what appears to be money ($) off a dead soldier before grabbing his gun. What I'd like to see is, money being used for things like guns, medicine, ammunition, grenades, equipment and what have you. While the diamond factor could be used to upgrade abilities such as: ammo capacity, range, carrying capacity, healing capacity, healing speed, night vision / infrared time (before outage), sprinting, underwater breathing, visibility, sneaking, (stealth) consumables.
This way, character customization can be handled with diamonds, while preparation can be handled with $, making a double monetary system which would make things more interesting in my opinion. Also, not everything would be available right away. Example: in order to unlock what you want, you are required to unlock the stuff preceding the branch, even if it's less useful, or you could skip getting what you really want at that time, and put those diamonds into making your character better in (x) way. Maybe once an Act is cleared, higher skills will be available to unlock like maybe the ability to carry an extra syringe, or take a few extra hits before going down, etcetera. Stuff like that.
One thing I loved about Far Cry 2 was that you could pretty much power up your guy from the get-go by finding as many diamonds as you wanted before getting into the game. How do you guys want the system to work?
Games I want: Armored Core V, Hitman 5, Last of Us, Ninja Gaiden III, Far Cry 3