MerchantVenturer
As you say this kind of thing is not uncommon in the USA, although such the "recruitment" of such Ambassadors tends to be in joint venture between the airport authority and the local tourism authorities. This, in my mind, sends out much more clearly the right signals that the staff are literally there for the passengers only and specifically there to help them with stuff like local tourist information, local transport etc.
In other words, to augment rather than replace airport-employed customer service staff.