Would it make the cleric class too powerful if Fire bolt progressed like the sneak attack of the rogue does and allowing their channel to do elemental damage instead of positive or negative energy.
Channel fire sounds like it would be about the same level of power as channel negative energy - a different range of creatures would be resistant to it.
Making fire bolt do more damage would be an obvious power boost. As a GM, I might allow a fire domain cleric a custom feat to do that.