"I'd always thought the same thing about using a poncho for both raingear and shelter - how do you get out?"
One alternative is to also carry a 1-ounce "emergency poncho" --- you have to search for something like this, and it's not meant for extended use, but can be used if you need to move around camp in the rain.
Pee bottle: on trips where I'm not sharing a tent or camping close to others, I'm a fan --- great in lots of rain, cold, or fierce bugs. There ARE options along this line for women. Obviously I have no direct experience, but a simple web search will turn up options.
You mentioned heat buildup in humidity in a bivy. While on occasion I love the ability to tuck into small places with a bivy, it's that sort of thing that drove me away for the most part. I recall one nice evening where the bugs were fierce yet it was just too warm to be in the bivy, even if on top of and not inside my sleeping bag.
For me, a water *resistant* very light bivy can be a good augment to a minimal shelter, particularly in shoulder season hiking, and that's about it. Note, however, that I'm a pretty indifferent (and infrequent) mountain climber.