As a followup to this, I told Guatham I would consider mentoring this (pending an actual GSoC project submission).
It would be nice to have a co-mentor who has better admin skills that me and ideally who has hosted "real" onion services in the past to provide perspective on use-cases and needs. I've only hosted txtorcon's documentation (and Git repository).
I told Guatham it would probably be worthwhile to consider that evan a moderately paranoid operator likely isn't going to want Python + Stem + gnuplot or whatever on their onion-hosting machine [although, obviously PHP is okay, right? ;)], so a lightweight and easy-to-audit "statistics collection" script and an offline "analyze and draw pretty pictures" program is probably the way to go...?