While I can accept that your intentions are honourable, did you stop to think that you are casting aspersions at a very capable and in many cases senior developers by suggesting that the reason they will not adopt C++ as an implementation language?
You are correct that there is a deal of inertia behind C as the implementation language for CPython, as indeed there should be. It represents a huge investment, and has created valuable artefacts. As someone who isn't a core developer but manages programmers professionally it seems to me that you are ignoring many easily detectable issues, some technical and some social.
- Who will put in the engineering effort to ensure that C++ code is supported within CPython codebase on all supported platforms?
- Who will create and maintain the extra tests this would require?
- Who will handle the inevitable deep bugs that the introduction of a not-fully-compatible technology will create?
- By how much would such a change enlarge the core developer community? I so far know of one person it would add—you! What's the return on the effort?
Remember, relatively few people are paid to work on CPython. Most do it for love and/or to scratch personal technical itches. What would they get out of the adoption of C++. While your enthusiasm is welcome, it's beginning to become a little wearing. Perhaps there's some history in the python-dev archives that would inform you of previous discussions and help you repeating already-considered arguments. I'm struggling to see the benefits here, and your presumption that experienced team members should immediately be persuaded by your arguments seems a little, well, presumptuous.