i have done nearly this. We decided which car we wanted, but went to a dealer to test drive it and check for comfort , fit , etc. We told the salesman what our plan was, so he just gave us the keys and told us to check it out. A few weeks later we made the decision, had a deal in hand, and went back to the guy that treated us right and told him the deal we had. Let him know that if he could match what we had, or give us reason for something better, then the sale was his, and that we returned only because he had treated us right on the first day.
Customer service can still win a sale, because as you say, there is a need for the consumers to actually see and touch the car in many cases.