There was a "Nature" program a few years ago about winter in Yellowstone, in which the naturalist was sleeping in a bivy under a tarp. Of course he was highly experienced and of course he had a TV crew with him (no mention of where the TV crew slept!). I certainly wouldn't recommend this type of gear to a beginner.

There are a number of floorless pyramid tents made by Mountain Laurel Designs, Oware, GoLite, Black Diamond and others, which will shed heavy snow and are a lot lighter than your standard 4-season tent. With a mosquito netting "nest" added, they are suitable for summer, too, although the tent/netting combo is definitely heavier than most tarptents.

The point here is that the OP has admitted his inexperience. If he's going out in winter, he needs to learn how to cope with all the hazards he will encounter and gain experience in the company of experienced winter backpackers. To start with, he'd probably feel more comfortable and possibly save money by renting or borrowing a winter tent. Once he's had winter camping experience and decides that he likes it, that's the time to consider investing and possibly going to a pyramidal tent.