I use the old British army issue canvas poncho for shelter and to sleep on top of it (as a sheet for an “A” frame basha). Works fine even though the buttons do not support the weight when lying on it. So I had to use my imagination and some twine to fix it…
I've seen the new issue one. Under closer inspection seems pretty goochie. Its lighter, no hood (which is a good thing), more attachment points, makes less noise and comes in DPM.
If you regard tents just as extra weight I would advice you to buy something like this. Having spent numerous nights under it I would not want to go back using a tent.
The poncho protects you from the rain, the sleeping bag provides the warmth and a roll matt provides the comfort.
Reinhardt