Ideas for creating a subsite directory

I have run in to a bit of trouble trying to develop a dynamic listing of all the registered subsites on my main site, and was hoping to get some ideas and feedback on ways this could be done.

So far my thoughts would be having the homepage of each site as a custom post type and then having a global display of the fields. The problem is that I don’t think the custom fields plugins ACF and Types work that way on a global level.

I know wpmudev has a site listing plugin, but I would need a great deal more information present than just the title so and ideas how to associate custom fields with the site information would be helpful if that is viable.

Any wordpress codex or custom functions anyone knows about that apply to this type of work is sincerely appreciated, I am not very good with WordPress yet