This is exactly what I consider an unwieldy workaround.
I mean, "I rejected the power of the god because the gods are evil and uncaring for the struggles of mortals, but oh, I will continue using spells anyway" even sounds weird. "...but hey, I found a new god to pray to! Overnight!" isn't noticeably better either. Even if the class itself was changed into fighter, well, that opens another can of worms: where the hell did cleric learn all the fighter's tricks? Why didn't she use any of them before?!
And then there's an issue that a sacrifice wasn't made, not really. In, say, Dungeon World, if you change your class, you can feasibly start from level 1, sacrificing all the cool things that a lvl10 character could for a clean slate without being totally useless. Your character still will be noticeably weaker, but not to the point where they are playing in a completely different league, which both a) makes sense b) doesn't necessitate learning how to play a high-level character of a completely different class.