how i can try?I did try just a few weeks ago and the problem does persist in the new image. I have an old lxc image I created a while ago (well converted from openvz) that I recently upgraded to jessie and it works great with systemd (it is a 32-bit and my new one is 64-bit if that makes a difference). I figured that if one worked maybe I could tweak the other to work.
[..]In order to get systemd working with DAB you must check the instructions mentioned at https://bitbucket.org/snippets/flybyte/GEpo8.[..]
You can use DAB (https://pve.proxmox.com/wiki/Debian_Appliance_Builder) to easily create your own Debian LXC template. I've put some example DAB templates on https://bitbucket.org/flybyte/dab-templates along with some information that should help you get started. In order to get systemd working with DAB you must check the instructions mentioned at https://bitbucket.org/snippets/flybyte/yjoMo.
As for the use of systemd in LXC, I've been using systemd for a couple of month now and never experienced any issues (Debian only). Not sure why the Proxmox team hardcoded the systemd exclusion in DAB but I'm sure they had their reasons. Luckily we can work around this.