Remove attachments is grayed out in Mail

I'd like to trash large attachments in my emails, while keeping the email, and the Remove Attachements option in the Messages drop-down menu is grayed out! I see, in searching, that this bug has existed now for 3 or 4 years, and since Apple's moved on, I assume it will now never be addressed. But had anyone ever found a decent workaround, to delete attachments?