Might be worthwhile having a Ptr parameter in the .set(...) method to pass user data to a State instance; not sure about the underlying code in the .set(...) method to know if this is a viable option.

You might be able to override the State class to add this functionality yourself... not sure though haven't looked at it to check. However in my opinion, keeping your global game data in one place in a constant memory address is a far better solution, as we discussed in your other thread.

I will certainly give it a go