It should be easy to set up: in a slightly different - but actually similar - raster context, I had to do update-retiling for a bunch of GeoTIFFs that cover an entire city, with different sets of geoTIFFs at different ranges of zoom from 9 to 18. The GeoTIFFs also didn't 'fit' neatly into TMS/Google Maps tile numbers.
Rather than re-tile the whole job (which took 19 hours for the full fileset), I set it up so that if a geoTIFF changed the renderer would
- identify the set of GMaps tile references that the 'changed' tile intersected at its lowest rendered zoom (that's easy since the bounds of GMaps tiles are fixed at each zoom - find the set of GMaps tiles that completely contain the bounds of the changed GeoTIFF);
- grab all GeoTIFFs from the same 'zoom set' that intersected the GMap tiles from (1) above; and
- make a new 'base' GeoTIFF by stitching together the geoTIFFs collected at (2) (making a vrt with gdal);
- tile the resultant vrt from lowest-zoom to highest-zoom for the geoTIFF in question.
The re-tiling never took more than a few minutes: that's heaps better than 19 hours.
With PostGIS data it should actually be way easier because there's no need to do raster comparisons and what-not - just need to find the basemap tiles that are affected at the lowest zoom level, and generate tiles for the bounding box of that tile and all its children (i.e., all higher zoom levels).
So if I were faced with your task (and not knowing what your basemap is - Google Maps, OSM, Bing, custom), I would identify what basemap tiles were impacted by the change to your data at the lowest level of zoom at which the data is presented, and re-tile everything in those tile and its children.
If you know
minZoom for the data in question, finding the base tile number is straightforward (there's awesome code by Klokan Petr Pridal on Tiles à la Google Maps that will enable you to find the TMS or GTile reference - and its bounds - for an arbitrary point... scroll down the page and look for a big text box. It helped me immensely with my task).
And yes, it ought to be able to be set up as a trigger: triggers can call e.g., Python scripts or other things that can do the yard-work for you.
Over the weekend I will try to dig out my old code and tweak it to make it more vector oriented (as I mentioned, this was a raster-based job).