The base version for uselessd is systemd-208, which is the version used in 13.1. Let's try if a direct substitution of the binaries works and watch out for the problems. Expected result of the project is to have a working package with "Conflicts: systemd" and "Provides: systemd". The goal is not to fix all problems, a stripped down system with uselessd is considered a good achievement. Anything more complicated could build on top of this.