RLS: Default slicer Selection

RLS , Restricts the data shown 

1. I have a silcer , allows the user to select a country 
2. I many different roles , some roles are restricted to one country , others can see all 
3. I can choose select all as default , will work perfect for some but a person with access to all countries will be greeted with an unsightly set of charts, if I choose a random country as default this will show nothing for Roles who do not have access

To accomodate for every role ideally I would like to set a default ,

I would define the default as the first country in the restricted dataset as defined by the role

i.e. Role A is restrited to Germany , default country is germany

i.e Role B is restricted to all countries, default Country is first country in the list

I am not sure if this will work , RLS will have to executed (the data restricted) then the Calculated Column execute ; I dont think we have control over the execution 

Maybe an option , 

1. Create a Custom Col called Default 
2. Function to getfirst Country in the list (assumption RLS is executed, before the function)
3. Have Default , checked within the slicer