network.protocol-handler.expose.sip -> Value -> false

Every laptop on our organization are installed with softphone apps which is x-lite. Thus, we had developing some portal on web to make it easier make some call. Basically the portal contains sip link with some number followed by colons. Our orginzation use Firefox ESR 52.7.3. To make firefox able to handle sip protocol, we add some configuration on about:config as bellow network.protocol-handler.expose.sip -> Value -> false After that, whenever our user click some sip link, the browser would triggered x-lite application. At the first time, the pop up launch application will be shown and then end user will choose default application to handle sip link. Our client running on Windows Machine. However, for our user to change about:config and choose default application launcher are hard to do. Hence we need to develop simply way to approach that. So we think to make a pre-configured Firefox ESR which is comes with custom build configuration and default launch application are the solution for our problem. I had read from several article that talk about deploying firefor for enterprise that comes with some configuration on default/pref as this link refer https://developer.mozilla.org/en-US/Firefox/Enterprise_deployment_before_60#Configuration. But the Firefox it self aren't ready to download. However, Is it that any possible way to pre-configured installed? How to customize the installer? Thanks