You don't need full node to generate Bitcoin address and there are plenty script on GitHub to do that.
About scalable, i guess you should find/create script which support multi-threading and written on lower (not low) level programming language such as C++.
et that bitpay is hostile towards Bitcoin
That's right, I need to create a bitcoin address for each user so they can deposit. Get notified about new deposit with addresses to be able to credit their accounts and then transfer Bitcoin from these addresses to our address. Do you have any recommends GitHub link?