Strange ticket management

In activity, you have both notions : Responsible and Assigned resources.
Responsible is the one who must make sure the work is done, and possibly coordinate different resources working on the activity.
Most of the time, the Responsible is also assigned to the task (in Project'Or RIA, the responsible is automatically assigned to the activity).
In all other items (Tickets, Actions, ....) there is only the notion of Responsible. It can be interpreted as the one who works on the item, but also as the one who must make sure the work is done, independently of who really does the work...

activity is something that is in original plan and ticket is unplaned effort according to type.

You're right !

Then for me the ticket and plan must be more linked (process, time estimation, record time pass...)

You're right, and that's why can sould define Planning Activity on the ticket : it mean it is the planned task the ticket is linked to.
Record expended time is a planned evolution, in stand by mode since quite long. I should wake it up . The main idea, is that user will just enter : I start work, then I stop work, and expended time will be automatically calculated. The work will be counted on the Planning Activity (as work, retrieving work from planned left work).
Time estimation is nbot planned but is a good idea...

Regards.