I've been wanting to build a site generator with unlimited page hierarchy in the past, but after finding that I could do it with Jekyll (I hate Jekyll, but it works) I also discovered that I wasn't using the unlimited page hierarchy as I imagined. It is difficult because you have to commit yourself to that hierarchy to not break the links later, and you don't always know exactly where to put each content.
Shameless plug: if you want themes for your site generator, you could join this effort I came up with while writing CMSes and page generators: http://fiatjaf.alhur.es/classless/showcase