OMG, I hadn't even thought of that. How I loathe subscription services. That would incentivize me to buy it outright while ordering for sure.
Even if they were to charge $100/mo for autopilot, there would still be a >4 year break-even on the current lump sum cost, and you could be earning interest or dividends on the cash in the meantime. Couple that with the ability to turn off the feature when you're out of town or not doing much freeway driving, and I'm beginning to think that I might prefer the subscription model.