Currently, a fixed set of statistic types is generated by StatGen. However, not all these statistics are interesting for every template. It would be better if the templates could register what types of statistics they need before starting the stats generation.
Large repositories, like the Linux kernel, often contain commits with bogus commit date (e.g., 1970-01-01 01:00:01 +0100, 2085-06-18 15:57:19 +0000, ...). At the moment these commits can be omitted using the --no-future and --max-age=<days> arguments. However, having an (opt-in) "automatic" mode would be nice.
Having more control over the limits, that are currently hard coded in the ParamsHelper, as well as the precision of the displayed data would make gitstats-rb more useful for large repositories.
Having a knob to switch to weekly precision instead of daily (for the global activity as well as the authors) would, for example, permit to show far more history in repositories like the Linux kernel.