This is a silly distinction. You can always include pre-built object files in your "source code" formula, then the build step is just linking it into an executable locally. That would bypass the quarantine attribute and effectively retain the ability to distribute pre-built binaries without gatekeeper getting involved.

Seems like only a matter of time before someone at Apple realizes this and takes the necessary measures to protect you from yourself.

The linking step isn't even required. You can download any existing binary and codesign it yourself with your local developer certificate. You can even overwrite the existing signature.

I assume brew could even automate this, but are choosing not to for whatever reason.