Set up urban deliveries on corners and in boxes like in apartment complexes. Of course, that would be perfect targets for little gangsta wannabes to break into and damage.
For those who don’t want their rural mailboxes smashed with baseball bats - buy two boxes, one larger than the other. Place the smaller one inside the larger one and pour cement into the space between. Your neighbors may have smashed boxes but the idiot will be easily identified as the guy who was admitted to the ER the night before with a broken arm.
When it comes right down to it what I see is a typical big government solution where a more individualized approach would be better.
In fact in my area our post office is in a 100+ year old rented building when there’s a brand new township owned building less than 25 yards away. We built a brand new building for our police department then disbanded the police department 2 years later.
What I would do locally is move the post office into the new building rent free. Triple the number of boxes and bring the people who live just outside the village limits into the post office instead of keeping them on a rural route. We have several hundred people around a small lake just outside the village limits (far more than are inside the village)
On the national level I would let the post office raise rates as needed.