I would like an option that blocks me from sending any email with an attachment.

Rationale - when I send attachments with personal information I should be sending links to files stored in cloud drives etc rather than as an attachment to the email.

This is to prevent data loss from third parties poor IT security related to the storage and management of emails. It also allows me to have more control over the access to the data.

However it is easy to be lazy and not follow this best practice. The block, when enabled, would nudge / push me to send attachments as cloud drive links by adding complexity to send the attachment.

You would probably need an option to temporarily switch this feature off (say 15 mins) as from time to time sending an attachment may be the only option.