1) How do you take off or put on your backpack while wearing the poncho?
2) Can you carry a 20" wide rolled CCF pad on top of your pack with the poncho deployed? Or is the portion that covers your backpack not wide enough for this?
1) With a small pack, just unzip one side of the poncho and slip your pack off. Quick and easy.
2) Carry the rolled pad vertical or insert in the pack if possible.
Regarding use as a groundsheet. Over time, any poncho is going to develop pin holes. So the question might be; do you really need a groundsheet? A water proof foam pad should suffice. Last weekend my gear was a 1/8" foam pad under a small NeoAir xLite under a quilt. I simply folded up the pad and carried in my Zero small. I only use it as a groundsheet when conditions warrant it.
The zPack poncho/groundsheet is much smaller than any poncho I have ever used. It actually does not cover all of my thigh, and it easy to hike or do chores in. In cold rain and skirt helps. My primary rain gear for all my backpacking life has been a poncho… and contrary to most, I don't understand how you can stand sweating in a rain jacket.