I like this idea. You mentioned netting. You could do a TarpTent (you can look at henry shires versions) style netting that is sewn to the perimeter of the tent around the bottom and sew netting to close up the front. Less fabric. It won't be modular but I bet you keep it under 20oz for the total.

I just stumbled upon this forum today. I love biking and backpacking. So this place looks right to me.

cheers,

Ron