I think it has already been discussed, probably a long time ago.
Basically, I don't want to use such an abstraction because it doesn't take advantage of each language's specific features. I prefer to have bindings that are fine-tuned and 100% compliant with the target language, that perfect clones of the C++ API in every language.
Experience on current bindings showed that many things need to be redesigned and customized according to the target language.