How in the world is a mail carrier going to deliver mail in a huge esprinter, you going to have them open their door and climb out at every mailbox?
This leaps to a conclusion. Probably the documents are public - why did they choose this solution over off-the-shelf options? (No point in speculation; what is their actual analysis?)
It's not. Offshoring critical infrastructure is always a bad idea.
they'd have to deal with EPA and NHTSA rules
Possibly not. They don't even have license plates, as the Postal Service outranks state governments.
Ford isn't selling the Transit Connect in North America anymore. And they're made in Europe, so despite the brand, they're a foreign vehicle, too.
What postal services are those? Are you sure you aren't confusing the USPS with a parcel service?