Note that there is Python for the i:
It's native (implemented in ILE-C), and faster than PASE-based ports of Python.
For me, Python on my PC is still much faster than iSeries Python on my
employer's ancient AS/400. A modern i ought to be more competitive.
But regardless of relative performance, obviously there are some
advantages to keeping everything on the i. In particular, automation
of tasks involving data that lives on the i is simpler when no other
machines are involved, and iSeries Python is faster than alternatives
such as REXX, and competitive with (perhaps even faster than)
alternatives such as Java.