Very nice writeup. You made me want to watch The Hobbit with all the dragon talk! It was a great analogy and really grabbed my attention haha. The words really just worked great together.. Dragon.. Scale...Gold(blockchain tech!)
I'm very excited for plasma. I've done a little bit of research on scalability while looking for investments since it's pretty obvious big blockchains are going to need scaling solutions! I'm sure you have heard of Raiden Network, but if not they are doing something pretty similar using payment channels. Combining sharding and channels would make for a wicked fast network.
I dig the little chart comparing BTC, PayPal, Visa - Its a great visualization! One million transactions per second would be insane. Just shows how powerful this technology is, that it could blow Visa(probably the most used and adopted payment network in the world) completely out of the water.
The cool thing is, all these technologies work together and can be used on both the parent and child chains.
Sharding, Raiden and Plasma
Vitalik has mentioned that he will be utilizing all of these methods working together to help scale ethereum. It does seem like he is leaning towards not really using Raiden Network though.
In one of his blog posts he talks about how these strategies complement each other and can work together, but also states that he wants to keep the scaling solution "within the ethereum family" and is recruiting people to help create a scaling solution. This is what leads me to believe that he is trying not to use them.
If you wanted to read about it, this is his blog post from early January: https://blog.ethereum.org/2018/01/02/ethereum-scalability-research-development-subsidy-programs/