An idea occurred to me today: a "recharge rate" inspiration, with the following ranks:
Shortens all cooldowns by 5%, with a maximum reduction of 15 seconds.
Shortens all cooldowns by 10%, with a maximum reduction of 30 seconds.
Shortens all cooldowns by 15%, with a maximum reduction of 60 seconds.
Obviously, those numbers are "from the hip" - they'll almost certainly have to be tweaked for game balance.
The graphic would be a grey box with the clock emblem used for recharge reduction enhancements, obviously.