WP Guru has two scripts to make this process easier at the above link maybe you can incorporate into your final script to make it easier if you do I'll post it on this site for free so everybody could download it for free
Not an expert, but.... a script works only within the program as far as i know. so a script that exports to an external website mixamo, where you got to make configurations yourself, downloads and imports the model might not be something that could be done.
I meant well the final product would include 2 scripts 1 to export the Genesis 2 FBX How WP guru says to do it in his tutorial to a specified folder ...and then the other one that you would use after you were import the fbx With the animation from mixamo... And the script would just do all the actions. WP gurus tutorial did After the part where the mixsMo animation was imported into daz studio... Or 2 make it simple if you could just write me a script that would convert a Mixamo animation to a Genesis 8/8.1 pose preset... I'll just pay you for that it'll be greater if it was a batch script... Cause I have a folder of like 2000 mixamo animations