I AM SATOSHI
If I wanted to create my own altcoin, what is the easiest/fastest/cheapest way to do it?
Duh, Satoshi wouldn't even ask those questions. He would already have all needed knowledge for that. He had a separate test chain with 20-bit difficulty blocks. More than that: he knew exactly, how to swap coins between different chains, in a trustless way.
If you're still worried about it, it's cryptographically possible to make a risk free trade. The two parties would set up transactions on both sides such that when they both sign the transactions, the second signer's signature triggers the release of both. The second signer can't release one without releasing the other.
And if you have that kind of knowledge, then for example you also know, how to create an altcoin in a way, where those features would be just built into the new protocol (so you wouldn't need any external tool, because you could then do the swaps directly from your wallet, without even bothering about listing your new coin on any exchange).