The USPS is already hemorrhaging cash and their service is extremely poor. I have approximately 3,000 pieces of mail per month for my company - NOT mailers, these are actual live checks, proceeds - and the failure rate is around 4.5%
Sure, blow some more cash on vehicles that nobody actually has a true total cost of ownership and dearly overpay while doing it. It is just a matter of time until UPS or FedEx or somebody else big makes the gubment an offer it can't refuse and then the mail will be "fixed". Until then, just keep arranging the deck chairs on the Titanic.