It may not be practical to do at home but Tesla has already demonstrated automatic battery swapping on their Model S. They've timed it at twice as fast as filling up a comparable luxury gas car:
California appears to be phasing out that requirement (ability to swap the pack), which is why battery swap stations are no longer being pursued aggressively.
http://articles.latimes.com/2013/may/05/business/la-fi-elect...
http://gas2.org/2014/07/02/ev-battery-swap-stations-may-be-a...
It had to be planned. I don't think it was feasible in the roadster because of the battery placement. But the model S has a nice flat battery on the bottom of the car, making for great weight distribution and easy access. I haven't seen any news of any actual swap stations though.
Also, I don't think that battery lifetimes can be stated with such certainty yet. Few electric cars have been running long enough to know just how the batteries age with that usage. About the closest available is the fleet of older Priuses that are hitting a decade or more on the road, and they seem to have occasional failures but not the consistent aging that's been predicted... but of course they use the battery completely differently, and capacity is less important.
Possible solutions:
1. Buy an extra Tesla battery and swap the batteries in the evening when you get home from work. I know this isn't presently practical [EDIT: at home without special equipment], but the idea of swapping electric car batteries is being discussed for the future, to avoid long charging times.
2. Buy an exotic and very efficient home battery bank to store the daylight solar energy until it can be delivered (as charging current) to the Tesla after dark.
3. Shame your employer into installing a solar changing station at your place of work. Emphasize the terrific public relations advantage, don't mention the cost.
Your suggestion of feeding the grid is by far the most practical approach, because it's already an option in many places.