I don't know the technical challenge of doing this, but allowing authors to voluntarily opt in to Lendink might save you the hassle of idiot authors who don't know the difference between "its" and "it's" and are just fine using "its'." Many authors like me want all the readers we can get and understand the terms by which we agree to let Amazon distribute our books.
Please build that site and I am in. I tried to explain to "horrified writers" that lending is legal and that authors voluntarily agree to lend books when they publish with Amazon, and that almost certainly loaning books will expand your sales and not diminish them, but why waste breath? If they don't want to loan, they don't have to publish with Amazon, or they can price lower than $2.99, simple as that. Those authors will be as hopelessly left behind as all the paper-sniffer fetishists.
Anyway, this is one of the things that happens when everybody with an Internet connection is a "published author." Whatever.