Sorry but I fail to see the point in that. The strong points of C++ are its compiled language and strong typing, which are not adequate for scripting. On the other half, GDScript is based on python because Python is a matured scripting language, with all the sugar syntax that are not in C. If you want to write in any case your game in C++, why bother with a slow scripting engine? Write directly the native components, you'll get the benefit of execution speed.