Possibly a dupe solution?

Well I remember back in WarZ being able to use SandBoxie to replicate the game and log two people in on the same server. Anyone got any solutions to this?

It doesn't work. I've tried it before. You need to be connected to Steam to be able to join a server and get authenticated. Using sandboxie to start up steam twice and run rust will only make 1 instance of rust show servers and the other won't show anything.

Maybe use cheat engine?

Don't think you can dupe with cheat engine, it's going to be client sided.