A question about perpetual rights.
Would it be a good idea to put something in the contract that states that the rights are perpetual, but that a writer can revoke this perpetual right by contacting us and letting us know that they want the rights back? For example if somebody wants to have their story removed from the anthology for any reason? Maybe with some kind of notice period? Or am I over complicating this?
Either the rights are perpetual or they aren't.
Yes, you CAN do that. But why? Why create more work for yourself? Because by allowing people to revoke that right, you create more work for yourself. You then need to unpublish the work, edit out the story, and republish it.
Which means on site where they automatically update the customer's purchase, the customer will lose the story they legally bought, because the updated version of the book will replace the previous version. While Amazon doesn't automatically push out new versions, many sites do.
This is where I draw a firm line in the sand. Because I am not creating more work for myself and I am not creating a situation where a customer is going to lose their legal copy of a work.
One could in theory republish the book as a different edition, right? Withdraw the first edition from sale and publish a different edition. That would preserve the version of the anthology that people had already bought.
That said, it still sounds like a nightmare in every other respect. That does make more work, just as you said, and a steadily shrinking anthology becomes a less and less viable product. It would be better to make a it a limited-time release and then unpublish it.
If it were me, I'd just make sure people knew that, though the rights being asked for are nonexclusive, the KU regulations would prohibit any of the included stories from being in KU. People could decide whether or not that was a deal-breaker for them.
The situation is not as it used to be. When I started publishing in 2012, a short story was still a viable product on its own, normally priced at $0.99. Now, however, with the wide range of free and cheap complete novels (not to mention $0.99 box sets!), the $0.99 short story just doesn't have that much appeal. Nor are they that attractive to KU readers, at least in my experience. A story could be in other anthologies, but from what I've seen, most of the cross-promotional ones are wide and permafree rather than being in KU, though there are exceptions. I'm thinking a writer isn't really giving that much up to let a story stay in an anthology. Being nonexclusive, it can still be used in other wide anthologies and as a reader magnet for email list-building.
The anthologies I joined are all wide and all perpetual. Interestingly, they still seem to get sales or free downloads, they continue to accumulate reviews, and the seasonal ones get a new lease on life when the appropriate season comes around. The exposure value is greatest at the beginning, but those anthologies are still attracting readers long after release. My stories get more eyes than they would have if I'd published them separately and stuck them in KU. I might add some or all of them into box sets later, being careful not to put the box in KU or forget that it's a mixed product and take it wide. (Yes, one of those rare beasts, the non-select, exclusive book.) The stories will function as a nice added bonus for buyers, and KU folks can still read all the novels in KU if they want. The fact that I can't put the stories themselves into KU won't be a problem for me one way or the other.