Firefox certificates policy and PAC settings

The Firefox certificates policy seem not to work in combination with PAC settings (proxy auto configuration script). So creating the policies.json file has no effect, a SSL/TLS cert issued from a private CA won’t be accepted. Even adding a root cert from a private CA to the cert store over the security settings doesn’t work while using PAC. Any solution known here, maybe even in accepting generally self-signed SSL/TLS certificates after check of their thumbprint?

Related bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=1764296