If you do a search for "fatigue" and my name, you should be able to find an entirely separate "Fatigue" mechanism that I proposed to replace exhaustion ... and yes, you could also use it to directly power Psions/etc if necessary ...
I went and looked, and found this:
http://www.ironcrown.com/ICEforums/index.php?topic=775.msg9975#msg9975
Is that what you were referring to?
I think that is the correct link. I very much liked the idea and have added it to my game with some modifications. Below I paste the current version of the rules that I use.
Exhaustion
*no exhaustion points are counted, instead rules for "pushing the limit" as detailed below are used.
*You have to beat your current Exhaustion Limit (EL) to keep going without (more?) penalties
*EL start at 50 and is increased by 10 for every period the character is pushing the limit. EL rolls are modified by the characters Co/Co/SD bonus.
*Failing to beat the EL will give you a exhaustion penalty until you rest
*exhaustion penalties are 0/-20/-40/-60/-80/-100...
*recovery time are 1 minute of rest or 3 minutes of normal activity. Each recovery period reduce your EL by 10 and move you one exhaustion class up(i.e. from -50 to -30).
* Adrenal-type maneuverer can be triggered without pushing the limits if the character is not pushing the limits for any other reason, and only for one round. After that round the character must push the limits to trigger Adrenals …
*Base stride is 12 meters per round, or 36 feet per round, or 2 meters per second, or 6 feet per second
* Combat - increases EL every 6 rounds (1 minute)
* Jogging (x2 pace) - increases EL every 6 rounds (1 minute)
* Running (x3 pace) - increases EL every 1 round
* Sprinting (x4 pace) - increases EL every 2 seconds
* Dashing (x5 pace) - increases EL every second
* You can accelerate at most one pace per second. This means it takes about five seconds to reach dashing speed. EL checks frequency depends on target speed and not the speed the character has reached so far.
*Additional Factors - Sleep Deprivation / Hunger / Long-term Exhaustion/ Sickness - forces the character to do EL roll even when rested. In severe cases the EL could start higher than 50.
(The above rules means the master sprinter with good stats need about 9 second for 100 meters, A newbee sprinter cover about 50 meters in the same time)