might be a stupid idea, but what if i carry a rain poncho anyway out of thin ripstop material and when i need to set up camp, just attach another piece of dcf or nylon to the poncho and use that as a overall bigger shelter/tarp/tent?
Usually the ponchos are too small to act as a sufficient tarp space, that's why

lightweight attachment for the 2 pieces and the tarp does become multi use again, or is it ultimately decided, that you need a rain poncho anyway to get out of your shelter while it is raining and the 2-in-1 solution does not work?

What if i carry an umbrella for that?

tried searching for the terms "combining tarps, or extra tarp panel" but could not find anything