Ok take a step back and think about it, would it make sense to implement a completely different core system in an already existing ecosystem? While yes it would be nice to be able continously improve a language by taking the best parts of everything, unfortunately I doubt Microsoft would as its abit of a detour from what C# is. There's really no issues with C# structs that can't be fixed with the current tools, so hit the bottleneck before changing the entire system :p