Hello Liviu
You ask me: At my school, teachers are divided into specialized groups, youth unions, .... So how to create the fastest ties for teachers in the same professional group or youth union to quit teaching? 1 works okay?
There is no exact solution. One possible trick is to make them work at the same time. If T1 has 10 activities and T2 has 12 activities, add all 22 activities in a constraint activities occupy max 12 time slots from selection (if each activity has duration 1). But this is stronger than what you need and might not work as needed.
OK, thank you Liviu