"In the United States, the PROTECT Act of 2003 made significant changes to the law regarding virtual child pornography. Any realistic appearing computer generated depiction that is indistinguishable from a depiction of an actual minor in sexual situations or engaging in sexual acts is illegal under 18 U.S.C. § 2252A."[1]
Maybe the government could get away with it, but if independent researchers did it, they could be charged with producing child porn.
Yes, Orwell's "thoughtcrime" is an actual criminal offense in the U.S.
[1] https://en.wikipedia.org/wiki/Simulated_child_pornography#Vi...