I don't see how your attorneys could argue against it.. GPU rigs, sure they should fall under the exemptions as they are freely programmable.
ASIC-based miners however are much like a cash register or hand-held/desktop calculator. Yes modern ones offer high flexibility in addressing their core functions but in the end they are fixed-purpose data devices and both are charged import duty.
Its not arguing the classification, that is the correct one. It is the filing and pressure of the exclusion to the 25%.