I'm working on it. I think I'll just remove the initscript without replacing it by a systemd unit.
When using systemd, reniced is partly redundant because a unit override is better suited to change nice level and IO priority of a service as this will automatically work on service restarts as well. I'll add a NEWS file describing the situation. I think reniced should nevertheless be kept as a package because I've heard of use-cases where reniced is run from a once-per-minute cronjob to keep user processes in check. This does not need any initscript and so the package will still have some use. Thanks for the notice and sorry for the wait Christian
