> different method/property/class/function that gives you iterators
> would be fine.

We already have such.  It's called itertools.islice().

If you had read the proposal, you’d know that was brought up, obviously.

I'm sorry, but you're missing the point here.  You and Christopher seem
to be having fun discussing this at great length, and that's fine.
However at this point I've not grasped the proposal and I've lost the
will to even contemplate the details. 

Fair enough — I need to update the proposal with the new details.

What I have grasped is that no
one else has offered much opinion, so saying that "everyone else has
agreed at every step of the way" doesn't actually have the weight it
pretends to.

Sure, but that was referring to a single point (changing how standard Sequence slicing would work), and it’s not how I would have phrased it. I might have said:

"no one has suggested otherwise"

If not one is proposing something, it doesn't much matter how many folks have been involved in the conversation :-)

As for not many people having contributed to the conversation, I'm a bit surprised -- there is a LOT of discussion about all kinds of ideas that are never going to see the light of day.

Maybe that's a good sign -- if people don't pile on to tell me why it's a bad idea, maybe it has a shot :-)

Or it's because I didn't put much text in email, but rather pointed to an external git repo.

If/when I can find the time, I'll updated my ideas and post again.