I switched this thread to the python-ideas list, since this is proposing a new feature.

On Mon, Oct 22, 2018 at 12:13 PM Sean Harrington <seanharr11@gmail.com> wrote:

I contend that multiprocessing.Pool is used most frequently with a single task. I am proposing a feature that enforces this invariant, optimizes task memory-footprints & thus serialization time, and preserves the well-established interface to Pool through subclassing.

We've got a disagreement over interface design. That's more easily discussed with concrete examples. In my own work, I often create a procmap or threadmap function to make that pattern more pleasant. Since you're making the proposal, why not share some examples of using Pool in the manner you'd like? As real a chunk of code as you're able to share publicly (and concisely).