How would you solve this issue?
Clearly separate the use cases. There's a "print something right now" case that can lead to endless output. Fix this to provide all the right defaults.
There's a "reprint some previous thing" case that is a special (non-standard) request where inputs can be checked carefully.
The input for date range cannot be auto-set to "today's date", as frequent back-printing is required.
False.
The input can be auto-set today with no effect at all on frequent back-printing requests.
What possible impact would a auto-set to "today's date" have on back-printing requests? Please enumerate them in the question.
The input for routes cannot be hard-coded, nor can it be deduced from routes that have already been shipped, because re-prints are required (see above).
False.
Reprints and back-prints are a special case. They never have default fields and are the exception, not the rule.