Lua isn't the only one in this space: I personally use Tcl (or Jim Tcl) for this sort of work, and it (IMHO) excels in this area. What advantages would you see your Python implementation having over Tcl or Lua which were designed with this area in mind?
Python is a much more popular language than Tcl or Lua. Embedding Python opens your application to scripting by many more people, because the average person wanting to write a script is more likely to be familiar with it. Even those familiar with multiple languages may prefer to use Python - Tcl and Lua are often considered to be slightly "quirky" languages.
Also, although an embedded Python interpreter is never going to run C libraries like NumPy, there are many pure-Python libraries out there which would potentially be available for scripts to use.
I don't think this is realistic, anyone who wants to script an application will use what ever is exposed by the developers no matter how bad it is (ie visual basic for applications, and redis with lua).