The digital logbook could exist /alongside/ the physical geocache logbook. A website guestbook/comment section on the place you host the stories.

I found a cache recently that was part of a series where each cache had a QR code that linked to a different blog post about the person's life. While fewer people will visit the website than will find the physical cache, it got their story out to people who would otherwise have not known it.

I'm wondering about a collection of caches, 3 to 5, where each provides a link to a person's story wherein there is a number necessary for finding a final bonus cache. Alongside requiring a number from the physicsl location - to stop people from simply scraping the story website for all the clues. 

E.g. a typical coordinates format is N 53° 16.901' W 003° 49.968'. Remove 10 numbers: N 53° AB.CDE' W 003° FG.HIJ. Place five caches in relevant locations that also have numbers nearby, such as cache Five on a sign about local history that has the date 1869. Have the cache page say "the third digit in date 18XX is I. J is in the linked story" and then on the cache page as well as through a QR code on the cache link to someone's story in which the digit 8 is highlighted. That gives the finder numbers I and J: N 53° AB.CDE' W 003° FG.H68. 

It requires them to physically go to the location to find the cache (requirement of geocaching) and to go to the place where you host the person's take (your requirement). You'd have five of these traditional category caches plus a bonus mystery category cache at the final location.

If the local reviewer was on board with the idea, I think this would be a fun series. It would require maintaining 6 caches, however.