It does not have to be an all-or-nothing affair. The USPS doesn't even provide vehicles to a lot of rural route carriers; they get a stipend and have to purcha

It does not have to be an all-or-nothing affair. The USPS doesn't even provide vehicles to a lot of rural route carriers; they get a stipend and have to purchase their own. They've been replacing LLVs with various sprinter vans and minivans for certain areas and route types. They recently solicited designs for a new mail truck and that should have included drivetrain flexibility. Major car manufacturers have been doing this for at least half a decade, designing cars that are built to take an ICE, hybrid, or EV drivetrain instead of an EV or hybrid drivetrain being shoe-horned into a body only intended for an ICE drivetrain.