Sounds like there may be a few things going on here:
1. Sales doesn't want someone contacted. Why? Is this because they don't want a "Buy now and get XX free" kind of promotion to hit their end user while they are in the sales process? If your marketing efforts aren't focused at the various conversion points in the funnel and might perhaps send conflicting offers to people sales is engaged with then why not give sales a means to suppress them from marketing via a lead/contact status. Something like 'in process' (or better yet, pull a filter using an integrated CRM/Eloqua by seeing who has linked opportunities). Clearly define what the status' mean (i.e. hibernate vs. do not market, etc.) so that sales can pull people out of the 'unsubscribed' mode if they do need to suppress them.
2. If the Sales team is really hearing requests for unsubscribes why not provide them a link to your preference center and allow them to talk their prospect through the opportunity to opt-down/change subscription preferences vs. losing them all together, or at the very least it allows sales to unsubscribe them in a scalable manner.