I could achieve this by overriding user edit page, this can be done as a plugin. you do not need to modify Q2A core file.
if($this->template == 'user'){ //lets first override user template and set our custom permission.
if(qa_get_state() == 'edit'){
$this->content['form_profile']['fields']['level']['options'][21] = Writer;
$form_profile_fields_level_options = $this->content['form_profile']['fields']['level']['options'];
}else{
if($this->content['raw']['account']['level'] == 21){
$this->content['form_profile']['fields']['level']['value'] = "Writer";
// Anything else you want to show on the profile.
}
}
// Then, say you want to override a question page and set certain permission for writer,
if($this->template == 'question'){
if(qa_get_logged_in_level() == 21){
// your code here.
}
}
hope that helps.