Возможно создать собственный виджет?
class FlattenJsonWidget(TextInput):
def render(self, name, value, attrs=None):
if not value is None:
parsed_val = ''
for k, v in dict(value):
parsed_val += " = ".join([k, v])
value = parsed_val
return super(FlattenJsonWidget, self).render(name, value, attrs)