I am not looking for binary compatibility. I am looking for feature parity. Go interfaces can be handled with concepts [1] or just macros. I am talking about an alternative Go implementation (i.e. just sitting on top of Nim), not ABI compat between the two runtimes.
Along that way is C++ and "we should attempt to be a superset of all programming paradigms". Fewer features is better, and more restrictions allow better tooling and iteration if they don't functionally restrict the programmer.
Basically, I'm not sure of the benefit of building go on top of nim. They appear to fill the same space in orthogonal ways.
1 - http://nim-lang.org/docs/manual.html#generics-concepts