@alexjoanroww I wouldn't consider changing a Sim to make them eligible as a BabyDaddy cheating. The
official rules that I follow say:
There are no restrictions on who can father children in this challenge but none of the donors can move into the household or provide any aid to your household whatsoever apart from impregnating your matriarch once. Using the child support feature of deaderpool’s Master Command Centre mod is strictly NOT allowed!
Making a Sim able to be a BabyDaddy doesn't make the challenge easier. It doesn't help your household in any way. I say it's fair!