Currently I would simply like to find all files that have not been modified in the last X days but ultimately I would like to be able to make more complex queries against my sub
Currently no, there's no subversion query language or query based api that's in widespread use (ok, now watch someone contradict me, that's life on the net I suppose).
This means you're limited to splicing together the outputs from the normal svn commands like
svn info
and
svn log
I'm sure something like bash or powershell could make this at least feasible. If you're stuck with windows batch, I'd start crying now.