Hey there, I also wrote an ebuild for Btsync - concentrating on getting systemd support right. My build has some attempted init.d support in it, but as I do not use init.d on any of my machines, I have no idea whether it works. I will try to follow your example to ensure that my ebuild properly supports init.d. You could also pull from me for systemd support. My ebuild is here, and I also wrote this nice tutorial/description for how my ebuild deals with systemd.