but didn't say anything about any kind of backend work being needed. Making a really nice Ponzi site?
Oh, did you read the basic requirements section?
The first work to be done is to make a choice on the right framework or library that allows us to connect node.js to a database (which can be MySQL or can be something that fits better to node.js) and then a library for having a user management using node.js and that database and which could use the bitcoin address as username. If nothing like this already exists it would be the first piece to be developed.
No. It is not going to be a ponzi scheme site. There will be real trading among the users and maybe the server.