Slavek,
I doubt you have had time to work on user session tracking in the pure systemd case. However, this is an issue I must get fixed or TDE is unusable on Arch (unless we ask users to manually kill all process that don't close)
Is there anything I can do to help? We have the kdebase-workspace patch from 4.11, have you made an attempt to apply it? If not, I suppose I could hand-edit/apply as much as I can, and then provide you with that if you think it will help.
Let me know if that would help or if there is something else I can do to help move this along. Thanks.