This is really interesting. How can you detect when it's the same person passing a captcha? I don't think IP addresses are of any use here as Anti-Captcha proxies everything to their customer's IP address.
Here's a fun experiment for someone: 1) Give N people K fake credit cards to enter into a form, and have them solve a captcha 2) Take recorded keyboard and mouse data similar to the captcha 3) Train a neural network model to identify
I've been out of this for 6 years but I bet transformers rock this problem now.