Good stuff. See wp-cli/cache-command#68 (comment) for an idea about how to get the information you need.

It might (???) be good to have your module call some sort of $wp_object_cache->usage_stats() function if it's defined. That could, at the option of the drop-in author, spit back some usage info for display in the module. There's a plain old ->stats() function but I don't think anybody calls it.

These ideas all involve persuading drop-in authors to add a few public functions.

Your proposal is fine as-is. I'm just brainstorming a few extra things, things I would use.

@OllieJones: I've talked with @johnbillion about this, since Query Monitor reads a lot of object caching metrics. We need a standard, ideally in core, that clearly outlines what's returned. We could even call it wp_cache_info()

@spacedmonkey: I'll gladly take this proposal.

we are working on this today at WCEU Contributor day