form class generator factory, because playing around in __init__ is grim.

forms.py

def generator(**kwargs):
    display_fields = ['field1', 'field2']
    
    qs = Model.objects.all()
    if 'instance' in kwargs and kwargs['instance']:
        qs = Model.objects.filter(type=kwargs['instance'].object_type)
        
    if 'request' in kwargs and kwargs['request']:
        if kwargs['request'].user.is_anonymous():
            display_fields.remove('field2')
            
    class MyForm(ModelForm):
        myfield = ModelChoiceField(queryset=qs)
        class Meta:
            fields = display_fields
    return MyForm
    
    
form = generator(data=request.GET, files=None, request=request)