The zippers you suggest for snow flaps would be subject to a relatively high amount of debris and might therefore fail. They would also add significant weight.

Only saying the downside to your suggestion. I've had some fairly negative experience with customer-service email, from companies that are otherwise careful and responsive. Maybe you ought to call them or something.

I have discontinued Mountain Hardwear tent with netting scrim around edges. Am not totally convinced of its utility, though its net door has been fairly well appreciated.

Also, just keeping doors closed would be same as offering netting on doors.

In hot weather, and strong sun, of course. keeping door zipped would be uncomfortable. I don't ultimately know the answer to all this.

One key however, when you shut door, or screen, is to kill all the buggers that infiltrate before they bite.

We're now thankfully past bug season until May or June.