I wouldnt mind not having prone if there were those secret tunnels you talked about. I think the "crouch" when you're sneaking can be used, feels kinda weird to have two crouch actions. Although on the topic of secret tunnels, there are some fairly secret holes that lead to falmer dungeons though

I got a nice little adventure with that. I thought the hole was just a hole at first.
I agree with the above post; there's not much use for prone position in ancient times i suppose

can't fire arrow, weird position to shoot spells. All you'd get are probably slashes to the knee.