The omission of blocked posts is done server-side by the app.bsky.feed.getPostThread endpoint, so you'd need to reimplement that to return the content of blocked posts instead, both upthread (parent) and downthread (replies). It would require acquiring and maintaining your own replica of the data, which is hundreds of gigabytes in size.
This is significantly more complex than making a few small changes to the frontend app.
This is significantly more complex than making a few small changes to the frontend app.