Yes a net keeps the mosquitos from biting but is nice to have an aparatus to keep it off your skin.You can hang it some way or carry some light poles for hoops. Is there any other way to do it?
Most sleeping pads and bags should be on a waterproof ground sheet. So now that is half a bivy.
If you sew in a pocket on the ground sheet to slip the bottom half of the sleeping bag and pad into, then you will not slip of the pad. Then put in another pocket to put what ever you use for a pillow into.
All that is left to do is put in some zippers to join the net to the ground sheet to keep out the ants and other crawling things. One thing leads to another all the time adding weight and more stuff.
I have got an expensive bivy but it is hot and does not breath good enough. To stay cool in hot summer, an all net tunnel bivy would be nice.