Eric, I reckon you could sew netting around the edges and add a center-opening bug door once you had your pitch sorted out. It would mean that you'd have to stick to one pitch height all the time, which would limit the versatility. I think a single-person inner net hanging from one or two of the inside hooks would be a better option. I need to push that to the top of my projects list, bug season is coming up fast.
As for door height, it really depends on the pitch. If you set the pole high and the sides high, you could have a very tall door. If you want the edges close to the ground, you can still have a taller door by creating a straighter ridgeline between the center pole and the upper guy point of the door. The edge corners by that door can be set close together, making a tall and narrow door, or up and further out, creating more space and ventilation.
It's hard to describe the differences in space fairly subtle variations in pitch and rigging will make.