Use subject instead of title for the name of an attached file

We send E-mails with PDF attachments and the final name of the attached file is the message title. We need the message subject instead with the ability to use smarty tokens. For example, the attached and merged file is 'Attestation BNSSA', I would need the name of file to be Certificat_BNSSA_-_John_DOE.pdf instead of Attestation_BNSSA.pdf I think it's more clear to use the subject as the the title because the title is more like an intern code like in CiviMail versus the subject that the recipient will see.

in the CiviRules screen, it would be great to have the choice whether to use the subject or the title to cover a wider range of user case, maybe with a checkbox Use: title or subject as name of the attached file.