tell that to Leica again... about huge plants... and Sigma... did you read reports from their plant (Imaging-Resource visited it)... it is anything but huge (http://www.imaging-resource.com/news/2013/09/19/a-geeks-tour-of-sigmas-aizu-lens-factory-precision-production-from-the-insi) = 50,000 square feet... Sony will not even blink to make 10 times bigger filled with the same equipment, that's not a question of the size - but the question of what you can sell to your market.
One thing's for sure - breaking into an established market with a captive audience is very difficult. People are already locked in to Canon and Nikon, so Sony can't simply rely on doing the same thing and expecting people to jump ship. People aren't about to dump $10-$50k worth of lenses to jump to a new system, for almost any reason.
They do produce a great sensor, though, and there's no technical reason they can't make third-party lenses focus just as fast on a Sony body as a native Sony lens. Indeed, it seems they've made strides in this direction on the A7rII. After all, all the camera needs to do is tell the lens to go forward or go back, and provide enough power for it to do so quickly - all the computing is done in the body using information from the sensor(s), with no input from the lens.
Sony is not going to win a market share of lenses by releasing bodies which only work properly with Sony lenses - that will just ensure that no-one buys the bodies either, with the exception of beginners and those who don't care about AF. They're only going to win it as current Nikon/Canon lenses gradually become obsolete and people replace them with Sony lenses. In order to do this, they'll have to release bodies which can use Canon/Nikon lenses to their full potential (in order to attract Canon/Nikon shooters into buying Sony bodies) and gradually release a comprehensive, high-quality set of lenses to go with it. Not just the common ones, not just lightweight/miniature lenses, but also specialised and larger lenses such as supertelephotos, f/2.8 zooms, f/1.4 primes and tilt-shifts, so that the Sony lineup becomes a credible alternative to Nikon/Canon for professional users. That way, people will start with Sony bodies, taking advantage of their features without having to replace their entire lens lineup, then gradually replace their Canon/Nikon lenses with Sony lenses as they become obsolete and as Sony becomes a more-and-more credible player in the camera business. You're never going to win market share by erecting a huge barrier for current users of other systems to switch to your new system - you need to make it as easy as possible.
