I think that an insurance policy for good samaritans would absolutely increase social goodwill and make people more inclined to help strangers. I think that creating a policy like this would draw attention to social issues and make people more aware of those who may be in need of assistance.
Yes, good Samaritans helping the elderly in China will most definitely increase social goodwill. Uninsured people need assistance when something happens, like illness or accident. If companies or the government can't or won't help, then good Samaritans stepping in is a great idea. People helping people is empowering and good for everyone.
Insurance gives some comfort and assurance. Without available insurance a number of professions and activities would not be performed. Although there may no be a lot of concern that one would get sued for good samaritan type activity there is always that chance. Have insurance available if that chance occurs would take one minor, though present, concern off the table.
Since China currently lacks a good Samaritan law, and there has apparently been a spate of extortion stories by those who actually tried to help people, hopefully this policy might increase social good will. It won't change human nature, but if it offers some protection to people who actually want to help others.