I hope your motto seekers are not overlooking the Latin phrases, e.g., the Brown University motto, In Deo Speramus, that are clearly part of the on-going conversation. (Two of your subscribers at least are Brown graduates; likewise, they are brothers.)

Method: would 18th century readers have perceived "In God We Trust" and "In God Is Our Trust" as so very different? We may be more attentive to such precision than most folks then. Beware too narrow a focus.