I believe you're over-thinking it. You don't need to install it in your floor, you could simply place it on top of your floor.

And it's not that hard to make it easy for people to line up - modern docks use a sort of fuzzy connector that doesn't need to lock in perfectly, just as long as you are within a certain range.

The roomba is the best example that I can think of for this - I can pretty much set my roomba down anywhere roughly on the dock, and it will start charging. I could definitely park my car with the same accuracy.