Dear Just,
The question is what causes what. Does the need for the activity of tefillah b’tzibbur cause the halachic allowance for porch minyanim, or; since this is a viable halachic minyan we activate it to achieve the great result of tefillah b’tzibbur. You seem to have said both. And they could both be true. But only one can be the justification for why we are having these minyanim.
If the only idea is that we need it so that our tefillos should be answered, I disagree. We are answered based on the merits of the tefillah. Creating minyanim solely for the purpose of having the koach of tefillah b’tzibbur is meaningless.
