Besides, what is the purpose of a timer in this game mode anyway?
It's to make you fight to win instead of only fighting to cheese feats. Getting 4 Fractures per battles is pretty good when you have only 5 minutes. But If you have no offence disks and lots of survivability disks, you could instead get all 40 in one battle at full stamina, and then you could vary your squads for the rest of the sector, never having needed to try to keep up your fracture rate with a 30% stamina Thrawn.
Actually, Leia, also: I don't use her for the fracture feat bc her ultimate takes too long to charge, and if I'm playing to win in 5 minutes and the Ult isn't charged for the first 3 or 4, by the time I get there I've killed a couple enemies and more of them are low health and killed by Leia's AoE. She simply gets fewer Fractures than Thrawn in the current mode.
But if you could play Leia for 40 minutes with lots of healing and no offence, you could repeatedly use her AoE fracture and slowly ramp her mastery (thus her damage) and eventually kill the enemy with only Leia doing damage. I completely changes the dynamic and makes energy cost per battle slightly less relevant and Stamina hardly relevant at all.