Yes, it would require additional people. If you did it by yourself, would you get in trouble still? Probably not - its still possible to do it by yourself, clean room just makes a stronger legal case for if they did come after you. But the engine is probably so complex you'll need other people to help you anyway.

Note this really only applied for Americans, correct me if im wrong but Reverse Engineering with no limitations is legal in the EU (software patents are also illegal in some parts of the EU, that i am certain of)