Cool magic trick but I fail to see anything useful coming out of it. I would not blindly rewrite code, rather see how it can be improved and maybe dig a bit in the existing functionality, clean it out, use the new language in my advantage...

Also as a programmer your mental modal is completely out of sync, how do you work on such application suddenly now that its all in Python (coming from C++)? Or is this shipped to a new team which received 100 000 lines of C++ but no clue how it all works?

How would FB use this at all?