I want to register 100k valid Apple IDs
Don't try to register more than 25 accounts in a day is my rule of thumb. Reach out to your Apple sales contact and work with Apple Professional Services or Apple Enterprise Support to create things and make sure you aren't covered with a tool / program to mass enroll or have your user base self-enroll in an efficient manner.

I've had good success getting our needs met across three organizations of differing sizes by reaching out to Apple for this need.