Love it. Makes complete sense...

Good idea, but already been done.
See here (Autopôle, under Services, 4th bullet point down)or here.
Sorry.

Is there an easy way of indicating and paying for such service? What if the wash was not satisfactory, or if there was a scratch that wasn't there before? Would there be an easy way of addressing these issues? The usual commuter wants to get in and out FAST --would the above negate this convenience?

Love it, but it's been done. Check out The Parking Spot in many U.S. cities. They do a great job.

Anthronify - to your point - the wash is always optional, no need to do it if you are only concerned about speed.

Gee, I guess I would hope it would always be optional. But if there is a random airport squeegie for me in the future, let me just say thanks --but please don't scratch my paint.

Is there an easy way of indicating and paying for such service?

Simple, you register with the company before hand, and they keep a log of what they did to your car, maybe by barcode or some indentifying means.

You can file a complaint online or in person at the office.