Borrowing quite a lot from the Agas, but simplifying and making more robust where I can, I'm slowly building a generic setup for displaying categorized GeoJSON features on the map. Once this is done, it'll be trivial to create new OL3 maps. I'm finding that the combination of namespacing and object-oriented practice is a bit tricky to pull off, and in particular, binding function parameters to events when they're constructed inside object methods requires some care -- using .bind() seems the cleanest approach.