In case it is still the concern of including Sway, in its early development stage, into the Debian Stretch release, holding it back from being packaged, this might no longer be an issue, as Debian Stretch is already in freeze, and it will take a couple more years until the next stable release.
BTW, I recently packaged Sway myself [1] for my PPA [2]. If it helps, you are free to use my debian/* files in Debian. But I suggest to remove the patch for linking libjson-c statically, which I just do in order to keep the same binary package compatible with a wide range of Debian/Ubuntu releases. I also build WLC as part of Sway and statically link it, which you might want to package separately instead. But then again, waycooler (another tiling WM for Wayland) always links WLC statically on purpose, so not sure if there is a point in providing WLC as separate package anyway. Sebastian [1]: https://github.com/snoack/sway/tree/debian/debian [2]: https://launchpad.net/~s.noack/+archive/ubuntu/ppa