Why don’t you just implement federation normally instead of taking this roundabout way of doing things? As long as your site contributes content back, and makes it clear where content is from, other projects like piefed and lemmy would be happy to have your project join the network.

Continuing like this will likely get you IP blocked from wherever you’re mirroring content from.

Also these platforms are open source. You are allowed to copy and modify things for your own projects, as long as you follow the basic rules in the license.