Having worked many years ago for Holiday Inn, I can say that if this is truly a small staff as OP surmised, it will not work very well. Let's say you have a staff of 20 mystery guests. How long do you think it will take before photos and/or names of the entire staff of mystery guests are shared amongst the franchisees? It's like the 10 Most Wanted poster! Front desk staff will be required to study those faces and then ensure that the loyalty program benefits are provided to the level of the mystery guest.
Of course, those GM's who train to provide the loyalty program standards will have nothing to worry about.