That isn't really much of an issue, some places count material intended to resemble a real child or derived from CSAM (etc a drawing referenced from real CSAM)

That isn't really much of an issue, some places count material intended to resemble a real child or derived from CSAM (etc a drawing referenced from real CSAM) as still being illegal. That would handily cover the situation you've mentioned. In those cases, for fictional CSAM to be legal, it has to be completely fictional such that any resemblances can be shown to be completely coincidence.