These are all the same questions you'd have to answer if you'd built the marketplace yourself, except the answers are even harder, and there's nobody there to c

These are all the same questions you'd have to answer if you'd built the marketplace yourself, except the answers are even harder, and there's nobody there to care when you solve them. And if you're on ethereum, you probably can use a 'different' coin easily, because it'll be wrapped or more likely implemented as a token, and you didn't have to do anything to get the benefit of that aspect of the ethereum ecosystem. Correcting/fixing wrong transactions is a fun one, but it's not impossible depending on how you set up your smart contract.