Not that its any fun, but making a standard vertex to bone weight painted rig for a face takes maybe about a day.
If you go the automated weight paint from bone envelope way that Blender (and other software) offer it takes even less since moving the bones in the proper places takes maybe 1 hour.
From there, you just create 52 poses to match ARKit’s documentation.
After you have the poses you convert them to morphs.
And you have a custom face, which closesly follows your actor actual performance, since when posing the 52 shapes you likely used HIS images as a reference…
The setup time, with the taking of actor photos, is maybe 8 hours.
The result is so much better than anything metahumans can offer that its not even funny.
And on top of it you don’t have issues with licensing or any other BS which may be part of the metahuman stuff.
So, again, what purpose do metahumans serve exactly?
None. Not even for learning material, since their vertex count is way over the top too…
(But then again many developers said this many times and were wholly ignored by epic. So obviously they don’t care. Since they can fake it like they have Daz Studio included with the engine for free, the meta humans could be even worse, and they still wouldnt care).