Log of deleted leads

There are a lot of times when companies need to regularly remove leads from Marketo after they have unsubscribed or are invalid to stay within their limit.

I understand that Marketo does not archive these leads, but it would be great if every time a lead was deleted, a log (just an exportable csv) was kept with the date/time, email address, and how lead was deleted (manual, name of campaign etc...)

This would be beneficial as part of an audit trail when leads should not have been deleted.