“My proposal is to lose the battery pack and replace it with big capacitors “
Capacitors lose voltage linearly as they discharge.
Capacitors would be much larger than batteries.
Capacitors would be much more expensive.
Tesla profit by 2020.
http://www.bloomberg.com/news/articles/2015-01-14/musk-says-tesla-s-china-sales-fell-no-profit-until-2020