I would NOFOLLOW all such links and tell anyone requesting additional takedowns to take a hike.
If you document anywhere on your site that the businesses can submit their own "manually reviewed links", I would HIGHLY recommend you remove any such wording. That in itself is "unnatural".
If you want to create an editorial link to another web site because it's good for your visitors, YOU should decide on the link text that YOU feel is most appropriate. The minute you let the site being linked to pick their own link text, title attribute value, etc., you've changed that link from a natural, editorial link to an unnatural link (similar to the way the target site picks their link text on other unnatural link building techniques where they "plant" links on other sites via directory submissions, article submissions, blog commenting, forum signature links and spamming, etc.)