Tell you what, buy disk mailers that have the proper aspect ratio. You'll find that the costs go way down.
The lesson is that if you don't care if the mailpiece goes through the automation machinery then you'll have to pay the manual distribution rates ~ and let me tell you, it costs a whale of a lot more to sort mail by hand than with those machines.
No, you see that's the way it works in the Communist countries. The government tells you how to do things and you do them that way, or else.
You beloved Postal "Service," would be out of business if they allowed competition. We always hear that we cannot allow competition because no business would deliver the mail to the Aleutian Islands because of the cost involved. Well, it costs them a lot less to deliver my disk to NYC than it does to deliver anything to the Aleutian Islands. They had been doing it for years at the the regular (inflated) first class rate.
As for your special mailers, I have them. They are "non-standard" and stiff too; and they cost about a buck a piece. My envelopes cost me about a nickel each. Only a government drone would make the suggestions that you have made to me.
ML/NJ