Hi
The two doors are really useful. Keeps you drier by not climbing around stuff, thus we do two doors in most designs.
For gravity style filters, I blow them out before I go to bed and stuff them in my sleeping bag. Not an infallible solution but it has served me well.
I've used the sawyers a lot, but if I I am not bivy hunting I may go back to the Platy system for ease of use / simplicity and speed