Can someone at least make a linter that ensures you only use a "safe" subset of C++?
The answer is essentially no, at least if you're seeking substantial levels of assurance or safety. Even the C++ Core Guidelines effort, https://github.com/isocpp/CppCoreGuidelines which is the closest thing to what you describe and is driven by influential members of the ISO C++ community including B. Stroustrup, does not claim that they'll be able to make C++ memory safe.