After reading some of the post in this thread, I have a few inputs that I would like to contribute. First my local SkyWarn Net Control does use the GR overlay of locations for spotters, as we get spotters from all over and we like to know who is in the area. Knowledge is power in this case if something like a pop up storm rolls in. So from my point of view, SN should continue with working out the bugs in the APRS to SN location issue.
Second, I do use APRS a lot, and when I'm spotting I find it better then using Cellular data. So I did a few test with my Digipeater and what is out on APRS-IS and found everything is working getting into the APRS-IS but as described does not seem to be making it to the SN output TXT file. However I do show up when I set a stationary location on SN.
I hope some of this helps, and I would be willing to work with/help SN get this figured out. I'm just not a programmer, but I do know how to work with Linux as that is what my digipeater uses (APRX). And just to be clear, I too am having issues with my APRS updating on SN