I wish, but no it can't be. Systemd disallows variables as the first argument to ExecStart, so it can't be set via an outside configuration file. This is currently set to a good path on F19-20 and EL7 (which are the only platforms where this file gets packaged currently). We will probably need to rethink the templating strategy when we need to support another systemd platform with a different scheme for pathing the java binaries.