A note on S.A.M.E. codes: The National Weather Service divides the United States into states and counties. Each county is assigned a six digit county code. The first digit identifies the county subdivision, the next two digits identify the state and the last three digits identify the county.
There is quite a bit of info on WX radios tied to repeaters at http://www.repeater-builder.com/tech-info/weather-radios.html
. Also, you might want to explore CAT Auto's repeater WX products at http://www.catauto.com/wx_products.html
As far as liability should a net not get called, or repeater failure, I doubt seriously that a judge would even let the case go forward. Could be wrong, but it would be hard for the complainant to prove that they had no other way to get weather info, considering you can get it on TV, broadcast radio, cellphones, email, etc, etc, etc.
As for having a small group doing SKYWARN, every good ground truth report is a help to the NWS. Radars can't see ground level.