It's trivial to write this program in C and it is a waste of memory to load up 50 MB of Python just to accomplish this simple task.
Writing my_init took much more time than you think, and I do not regret choosing Python. My_init not only handles process reaping, but also environment variable handling and bunch of other stuff. Writing text parsers in C is a huge pain (libc has no regexps that are as easy to use as Python).
I do not oppose rewriting it in C, but given limited manpower and the tiny benefits it's not high on my todo list either. If you are worried about resource usage, then I would very much welcome contributions for rewriting it in C.
Or if you want small have a look here for minimal PID 1 "So how should init be done right?" http://ewontfix.com/14/
The environment variable handling and other stuff could perhaps be handled in a separate bash-script (or Python), such that the scope of the actual reaper is sufficiently small (to use a lower-level language).
There comes a point where you have to take a look at the diminishing returns and say "That's good enough."