Staying with the proposed heat-absorber as a basis, here are a few suggestions:
Reaction Healing (Source [heat], Limited to absorbed heat rank, Self only) 2p/rank
This costs the same as vanilla Healing, while it requires a sufficiently strong external heat source to work, it requires no effort on the hero's part (it functions automatically).
Enhanced Strength (Limited to absorbed heat rank, Fades) 1p/2ranks
Being subjected to strong heat boosts your strength, but every turn you use that extra strength you'll lose 1 rank - until you recharge it by absorbing heat again.
Ranged Damage (heat; Limited to absorbed heat rank, Fades) 1p/2ranks
This effectively works the same as the "Heat-Power" example above, you can discharge the stored heat as targeted blasts, losing 1 rank after every shot (til you recharge).
- The reason for the latter 2 lacking a separate Source (heat) flaw is because they already have Fades - they both keep functioning for a time even when not subjected to heat anymore. Here "Source (heat)" is only a descriptor for the recharging condition of the Fades flaw (and it also tweaks the rules for Fades a little, meaning the power can be recharged at any time under the right conditions, even during combat. Therefore, no extra Source flaw.
- "Limited to absorbed heat rank" means that the effective rank is capped by the equivalent ranks of the heat absorbed, while the theoretical maximum is the rank you paid for. So when you've got 10 ranks of "Heat-Power" and got hit by a military flamethrower (rank 6 heat damage), you'd get only 6 ranks of Enhanced Strength.