When you see an offer for single server up to 4u being offered does this mean that it can be a 2u server with a 2u storage bay attached, 2 separate devices, but 1 server. Or does it have to be a 4u case?
It's usually one server that can be up to 4U. Most facilities that offer this will then provide a single PDU and switch port for that one device. From there, more power / network drops can be purchased separately.
I bet nothing is stopping you from stuffing a 4U case with a small switch + as many motherboards, power supplies, etc you can physically jam into it. Just make sure the backplane looks "normal"...