I believe the U.S. Postal Service is an essential service for mail and I also think that mail-in voting is perfectly fine, having done it in Washington state for 20 years. However, the USPS should also be self-sufficient by consistently upgrading its service and operations with the changing times.
I see no problem in adding or decreasing drop boxes based on need, especially when other stores like PostalAnnex and the UPS Store take letters for delivery. Nor do I need my mail six times a week. Three days should be sufficient for mail, and if something is urgent use another means of delivery, like FedEx or UPS.
The USPS can also handle the volume of mail-in ballots given that they consistently handle half a billion Christmas cards every year. Bottom line: Keep the USPS, improve operations and don’t pass an unnecessary $25 billion to shore up operations on an inefficient organization.