Folks should have the ability to unsubscribe from all e-mail notifications from all projects in a bundle whenever they purchase a large bundle. It's infeasible to unsub from each and every project manually as each individual project sends out an e-mail to their buyers. Either a 'unsub from all mailing lists' button or a 'unsub from all mailing lists included in bundles this project is attached to' (but, y'know, more concisely stated).
On the creator-side we also can't discriminate on who we're sending e-mails to, so I can't exclude purchasers from a bundle from who I'm sending e-mails to. Improvements on this system would likely greatly increase the value of the e-mail system in general as folks would be more in control of their messaging and therefore more likely to engage.