I will call it Faith because I have a Paladin in mind, but this could work with any type class.
To generate Faith you would have to deal and take damage, much like Barb, but Faith does not go down with time so you could easily ride on max resource if you want.
None of the skills would generate or cost Faith in its base form, they would rely heavily on cooldowns.
On one of the possible upgrades for the skill there would be a Faith cost in the form of “if spend X gains effect” (garantee crit, status effects, buffs, less/no cooldown). This effect could be stackable like “for every X spent gain more effect up to Y” (fortify, area of effect, buff time) or conditional like “if Overpower deal Y more damage per X spent”.
Also, some of the passives would give benefits for a constant small consumption of Faith. Like “every Y sec consumes X Faith for benefit” (cooldown reduction, move speed, increase crit chance, remove CCs, block change, etc…).
This would allow the players to choose which skill would have costs and which would not. Giving the option to focus on what you want to happen and when.
The class specific powers are Auras (off course). They would work like the passives, but they would be huge bonuses for huge consumption. And there would be no limit to the amount of Auras active. These Auras could also be customizable. Like the Holy Aura can be modified to do Holy, Fire or Shock damage.
So, what are your thoughts about it? Any suggestions?