I’m fiddling around trying to change the Nav Data overlay, at least to make it have a few more options. The general mechanism is that it grabs tiles from http://openaip.net/ and puts them in as an overlay in leaflet.js (a browser map tiler engine). The server is a little util written in Go (basically just bridges SimConnect for position) so the ‘meat’ is the html/js of the iframe within the panel. I might be able to pass some options to the openaip.net map display to get what I want.
You might be interested @Aginor that it has a Soaring mode, where it will show thermal hotspots 
