Since he used to be the ideal Lynn wanted Rod to aspire to, it's sort of obvious that she'd need an avatar for someone blundering his way through being a step-parent. It seems to me that said avatar is Connie. Next year's arc sort of proves that point when we see her be confused by the fact that Lawrence doesn't actually want to share her with some new person just because Mommy has needs. We who think about the issue without the need to make villains of children can relate to his desire to not want to have change imposed on him without his consent and not screw up like Connie (and probably Rod) by taking it personally. After all, human nature mandates that the new person in the equation be the villain of the piece selfishly introducing disharmony because he or she is an arrogant jerk tricking the 'real' parent into doing bad things so it's sort of incumbent on the parent to actually BE an adult instead of a child whining because his or her ego has been bruised.
The problem is that it so turns out that this is more than Connie ever managed to deliver while Molly and Gayle were still part of the cast. We could have seen her either grow into the step-parent role or, as happened in the retcons, learn to build a friendship with them after they're out of the house and they learn to see her for the messed-up and terrified person she actually was instead of the manipulator they needed to see her as. This is probably where Rod and Aaron are now, by the way. They don't seem to be close and probably might never be but it's likely that they've probably stopped resenting one another's presence.