I’m not sure how it solves the FFI problem. Lowest common denominator calling conventions don’t make it any easier to bridge languages than it already is.

C calling conventions are already the standard for FFI in native code, and that means dropping down to what can be expressed in C if you want to cross that boundary.

As far as Go is concerned, the Wasm sandbox makes the (addressable, C) stack explicit, which solves at least some of the issues CGO has to deal with.

It's not a panacea, though; it introduces other issues.