Hi Stephan
I took a look at your personal web site. Your PhD sounds interesting. Quantum coherence and photosynthesis. But off-topic here. (Sadly, personal web sites are a bit of mess.)
You wrote:
I'd really like to move this proposal forward in some form.
+10
As a next step, would it be helpful to summarize the use cases and reasoning in a PEP?
0
Here's my two cents worth of opinion.
By all means start a PEP (on github) if you find it helps you. I think it's too early.
If this problem has a pure Python solution, then I think it best to develop it as a third party module. I suggest the name slicetools. When slicetools is established, has users and is stable. That would be the time to submit the PEP. I think it would give a smoother and easier path.
For example, PEP 428 proposes the inclusion of a third-party module, pathlib, in the standard library. https://mail.python.org/pipermail/python-ideas/2018-July/052255.html https://www.python.org/dev/peps/pep-0428/
For more on my general approach to building a third-party library, see my posts. https://mail.python.org/pipermail/python-ideas/2018-July/052464.html https://mail.python.org/pipermail/python-ideas/2018-July/052470.html
That's the end of my two cents.
Oh, and those who have time and energy to contribute. They get the biggest vote.
best regards