There are lots of analytics platforms (Piwik, MixPanel, keen.io, GA), but they all have their own pre-made reporting, or are restricted in the data you can get out. For a low traffic volume, high visitor value site, we want to be able to query visitor/pageview/events to answer specific questions.

Does anyone know of a platform/library that does this so we don't have to build from scratch? Ideally JS based, as some pages are built using different stacks.