Hi,
We are a group of experience Android design, Linux Windows programmer and we will like to help you with the project.
DNS change is actually not that complicated and what we can do is write a script(as .exe) for you which you can call inside your NSIS code with parameters(new DNS's IP address etc) and script will do the rest. We will be glad to send you a sample of the code for you to test.
Do let us know what you think.
Sincerely,
Splash Lab Team