While building my Little Free Library, I came upon the idea of adding a dedicated hatch and container built into the library itself. I think it turned out quite well! The challenge, of course, is the threat of muggles disturbing the cache. Hopefully this will not be an issue.
I would love for this cache to be a Travel Bug hotel, but I would imagine that this cache has a high chance at being muggled. So deposit Travel Bugs at your own discretion.