I am not sure you understand the consolidation of regional centers that have already occurred, but that is another story. The number of “major warehouses” is shrinking for the USPS.So?
They don't need "refrigerated trucks", they need to have "freezers" at major warehouses to store stuff for an extra day or two. That's not a major cost, it's an incremental cost for unusual packages.
Adding “freezers” to a system struggling is not the way to keep costs down.