Electracity, I use humor here because your statement is silly. In order to double production capability with the current number of shifts, Tesla could not use the previous body in white line and final assembly line. A great deal of work was needed to speed up the final assembly line as was witnessed in recent months, and the BIW #1 line certainly cannot double its output. What you need is a BIW line such as the #2 which is producing X at this moment with its great increase in number of robots. In order to double production capability an entirely new production line would need to be created (and was) but until recently when X started running smoothly it is probably not a good idea to move S to the new line as well. Building a new production line which is way out of sync with demand would be foolish.
What we've seen at Tesla is incremental increases in production capability and levers pulled to keep demand in line with production capability. Demand levers for Model S pulled in the past included the introduction of right-hand drive, introduction of Tesla to new countries, the 70D which much value contained in the package, owner incentive program, introduction of autopilot (a huge lever, btw), and more-recently the Model S redesign. Future levers include introduction of Model S to Korea and numerous other countries, approaching scaling down of U.S. federal tax credit sometime in late 2017 or 2018, autopilot hardware upgrades to make S compatible with autonomous driving, more robust supercharger networks, more stores and service centers, and the list goes on and on. My point is that by taking factory tours and by studying what Tesla says, a person doesn't need to be a factory expert to understand the strategy. The advantage of such a strategy is that it keeps the waiting time down for ordering and receiving a new Model S. It's not coincidence that Model S orders keep growing but at a rate that is consistent with production capabilities, it is planning.
If your point is that by doubling production capability but not pulling appropriate demand levers production capability could exceed demand at that moment, then I would agree with you. But what's the point of such an academic exercise when we can see Tesla's methodology quite clearly, it has been working and will likely keep on working until they run out of new demand levers to pull? By the time they start running low on new demand levers, Model 3 will be in volume production and growth of S deliveries will become unimportant.
And so I repeat myself. Saying that there is a demand problem with Model S is silly. Demand is being carefully managed through demand levers to stay a bit ahead of production capability (which is growing about 50% per year, as planned), and this is the most intelligent way to produce made-to-order vehicles.