> As the legacy cmd.exe can be easily replaced, that leaves python.exe. 

python.exe is a console application, which attaches to a console session. Since Windows 7, each console session is hosted by an instance of conhost.exe.

The CMD shell (cmd.exe) is a console application, the same as python.exe. It doesn't matter whether Python allocates a new console or inherits it from another process such as cmd.exe.

> Likely needs to be configured via readline or its analog used under 
> Windows.

pyreadline implements readline for the Windows console API via ctypes. It supports Ctrl+L to clear the screen, including the scrollback. PSReadLine in PowerShell implements Ctrl+L without clearing the scrollback. That's a better example to follow if someone wants to take up the ambitious project of supporting readline for Windows in the standard library.