In other words, when J.W.'s are asked what their religion is, they should reply "Christian," not J.W.
Yes, on a form like a census or such like that asks for 'Religion', a JW would simply say 'Christian'. Same as a Catholic, Episcopalian or Baptist etc would put.
I would say that the next-step down descriptively for a JW would be? to say non-trinitarian Christian?
How about non-trinitarian low-church Christian?
That could be expanded to evangelical non-trinitarian low-church Christian?
Or even evangelical fundamental non-trinitarian low-church Christian?