Certainly which frame is being executed is an implementation detail, and I can see an argument from that that we shouldn't have a frame introspection API at all... but we do have one, and it has some pretty important use cases, like traceback printing. Obviously most people shouldn't be touching this API at all, but if you do need it then it IMO should be as useful as possible.

I don't see a better way to handle my (admittedly a bit weird) control-C case within the interpreter; I'd be interested to hear what you have in mind. But even if there is a nice way to fix control-C, then the proposal here would still be useful for e.g. giving better tracebacks.