Bad design stays bad design: the hope that pids don't get reused soon
breaks two assumptions:
1) I don't have to wait() for a child process soon. It's the programs
business.
2) Pids cycle: there are security patches to make pids of future
processes hard to predict by assigning random free pids.

I actually was about to report a bug on subprocess when I bumped into
this one. My problem is pretty thread-less but related:
How do I kill() a process if it's pid got recycled behind my back??

In my opinion the module should work the "Python" way of doing things,
otherwise programmers will be surprised, as I was:
a) don't do my work (no wait() for things I care of/have reference to)
b) do your work (clean up things I don't care of/have no reference to)

If that's not possible, how does subprocess actually "intends to replace
os.spawn*"? [Library Reference]

It is still possible to extend the Popen() call to reflect if the caller
wants a P_NOWAITO or P_NOWAIT behavior, but the closer we get to the os,
the less sense does it make to replace some other modules...