Project activities and tasks assignments

 In Project Management, I have created a project template with :
 WBS1 --> Activity1 --> Task1.1 & Task1.2  and
WBS2 --> Activity2 --> Task2.1 & Task2.2
I have selected "Role1" as "Lead Role" for Activity1 & Activity2 and
In "Assignments": I have selected 2 roles: "Role1" & "Partner"  and finally I checked the box "Leader SignOff" for both activities.
I have created the user logons:  TaskLeader1 & TaskLeader2 , user1, user2, user3, user4.
When I create a new project using my template, what I want to achieve is to assign:

             TaskLeader1 as “Lead Role” for Activity1
             Task1.1 to user1 and Task2.1 to user2

             TaskLeader2 as “Lead Role” for Activity2
             Task2.1 to user3 and Task2.2 to user4

I have tried but noticed:
1. Whoever is first on the list of assignees for an activity is picked as Leader regardless of the role.
2. You can add more than 1 assignee in “assignments” but then all assignees receive all the tasks in their inBasket.

How to implement it and get the desired outcome?

Many thanks for your help.