Policy-based sanitizable signature schemes (PB3S) allow a signer to grant modification/sanitization rights for a signed message to future sanitizers who possess attributes that satisfy a modification policy. Existing PBSS proposals use restrictive modification policies that only specify which parts of the message authorized sanitizers can modify, without giving the signer control over the modification content. In this work, we introduce an Extended Policy-based Sanitizable Signature Scheme (EP3S), which expands the signer’s control over the modification policy to include not only who can sanitize which parts of a message but also what specific message modifications are permitted. Additionally, EP3S enables the signer to define multiple modification policies for the same message and allows authorized sanitizers to delegate their sanitization rights to others with additional restrictions. We present a generic construction for EP3S using traceable policy-based signatures and a ciphertext-policy attribute-based encryption scheme, and we prove that it meets the security notions of PB3S. Finally, we propose a concrete instantiation of EP3S, analyze its efficiency, and compare it with existing PBSS schemes.