So it seems there actually aren't many barriers to entry at all. There's certainly a lot of legal questions, but if it's this easy to create your own model then it's hard to enforce anything…
I don't think there are actually major legal concerns. Copyright protects reproduction of a specific image. Looking at an image and producing something in a similar style is not copyright infringement, it's called being an artist. The law on this seems pretty clear.
The UK recently announced plans to make this completely explicit, to remove any remaining doubt:
"For text and data mining, we plan to introduce a new copyright and database exception which allows TDM for any purpose. Rights holders will still have safeguards to protect their content, including a requirement for lawful access."
I was wondering about trademark issues with a model that can draw new pictures of Mickey Mouse/Homer Simpson/Hatsune Miku if prompted with their names.
So it seems there actually aren't many barriers to entry at all. There's certainly a lot of legal questions, but if it's this easy to create your own model then it's hard to enforce anything…