That's what I was originally thinking of as the minimum viable product in my DARPA Grand Challenge days. Mostly for rental cars at airports. If you'd booked a rental car, one would arrive at the terminal ready for use, and you'd get in and drive away manually. For airport departure, you'd leave the vehicle at the terminal, and it would slowly drive itself back to the rental lot.
No need to go faster than 20 MPH, and you could put markers and sensors in the roads if necessary.
There's been too little done with slow-speed automatic driving. Google made their little bubble car, but dropped that product. There are some fully automated shuttle buses, but that's a tiny business. About 25 companies are in that business, but other than Baidu, few have any deployments beyond test scale.
This is an approach that is doomed to fail, because trying to hardcode the particulars of a specific route will converge to working pretty well until the moment something completely unexpected happens which needs human-level AI to be able to handle in the moment.
This is why level 5 autopilot isn't really going to happen without the invention of real AI, which is debatable whether that'll ever be achieved. Most certainly not in any of the timeframes Musk keeps promising.
1. FSD in certain parking lots. Make deals with some major stores that tend to have big parking lots (such Walmart, Target, Home Depot) to map their parking lots and designate specific areas for rider drop off and for unattended parking. Special signage or road markings would be added to the parking lot to identify these areas and how to move between them.
You can drive to one of these lots, go to the drop off area, and get out of your car. The car then can drive itself to the designated parking area while you go in and shop. When you are done, you can summon it and it drives back to the drop off area to get you.
2. FSD on certain stretches of major freeways. E.g., I-10 between Santa Monica and near downtown Los Angeles, or I-5 from where 99 splits off south of Bakersfield up to where the 580 starts and then up that a ways.
3. A service where for a monthly subscription you get FSD or close to it but only on trips between specific points, such as between your home and office.
The way it would work is that you would drive the route several times and the car records it and uploads it to the company. They use that uploaded data to test their FSD software to see if it can handle that particular route, and tweak it as necessary to either handle places it was having trouble or to hard-code special rules.
If the car notices that something has changed and it isn't sure it can handle it, you have to go back to manual driving and the car uploads footage and sensor data and the company fixes it.
Each route would probably have a setup fee and a monthly maintenance fee.