For me there are only two possible options:
In my personal opinion and as I only know about artist that hated on danbooru, because we´re hiding stuff behind a paywall, I think the best way to be kinda "fair" to them is, by making banned/paid stuff Builders+. As Zapdos already mentioned, it´s kinda "theft" taking money from people for stuff we didn´t make to let them see it. This only applies to gold and platinum users, while being a builder isn´t about paying. It´s about improving the website, either by tagging, translating, uploading and so on. People don´t work on Danbooru for a year or more, just to search and upload banned/paid images. And even if there are Builders who upload paid_images, it´s easier to check on them, warning them, etc. than to penalize users who paid for danbooru.
On another matter: IMO banned artist should be Builders+ anyway, even if we change nothing about paid-rewards.
(I would also be fine with admin+, if that´s the option evazion wants it to be, because I´m only interested in those images like.. a little)
But I also know, that Evazion is not a friend of this option, so I´m goin for the second possible way:
It´s also not very user friendly, starting gettin rid of those images, because there´s some angst that people with shit on danbooru in twitter-manners. There are alot of websites still uploading stuff they shouldn´t, not givin a damn about what the artist wants. If artists wants their stuff hard-deleted, then we can still do that, like evaz did some time ago. It´s not like we´re a super evil company, tryin to get all the money and penalize artist with that. We are able to work with them. Also, a argument made by evaz was, that we don´t know what artist are okay with and what they want to be deleted, so it would be better to wait for any artist to demand a deletion, rather than to delete it, just to be artist friendly.
And maybe, we should penalize members who upload paid-rewards more, if we are so eager to do something about that problem.