Hybrid (List+Dict) container in C++11

I am in the final stages of rewriting a C++ Python wrapper.

In Python everything is a PyObject, and I have an Object class wrapping a PyObject*.

I've provided [] access. If the underlying PyObject is a dictionary, ob["key"] will retrieve its value, on the other hand if it is a sequence type, ob[42] retrieves the value.

I now want to provide for(auto x:X) type syntax.

The original project (PyCXX) comprised a base Object class, and for each Python Type derived an associated class.

Sequence types (list,tuple, set) would derive from a Sequence class, and dictionary would have a Dict class.

The Sequence class contains the machinery for a stdlib vector type container (code here). Similarly, the Dict class contains the machinery for a std::map type container (code here).

I apologise that the code is messy -- in due course I will clean it up and present it at the bottom of this question.

I would like to attempt something ambitious -- to provide functionality for both of these container types within the same Object class.

So, if the underlying PyObject is a sequence type, we can do things like: for(auto x:X), and similarly we can apply a stdlib sorting algorithm for a dictionary type.

I would like to know in advance whether this is possible, practical, ill-advised, etc.

I'm not worried about designing something that if used improperly would crash or cause undefined behaviour. My concern is to design something that if used properly provides an effortless bridge between C++ and Python.

If this is indeed possible, might someone be willing to draft a basic roadmap?

If it is impossible, a clear exposition of why would help me towards a practical ultimate design.