As to your first question, unfortunately no
local keeps it within it's own scope wether it is file or function or whatever. You could however define a function in global namespace that can access it for you. The data is still there just restricted. I'm not entirely sure if that is what you were hoping for :/
As to the second question: I'm not sure you can subclass directly like that but I thought there was a way to define a control that inherits from another control? Would that work?