Suggestions for streamers.

Could you describe in detail what your dream stream would look like?

Okay. I'll base my answer on your points.

1. It would be nice to have information about when the stream will continue (when the opponent returns), I agree with that.
Regarding "finishing the save." How often do you come to the very beginning of the stream? I don't see a significant difference between "continuing from a save" and "joining in the middle of the stream." In a short time, you can usually get a good enough understanding of what happened to comfortably continue watching. In the worst case, you can ask the streamer or the chat about what's going on.

2. I enjoy watching when players interact with each other quite closely and have many options at their disposal (resources, powerful spells, control) and, therefore, many possible further actions. An important factor is also intrigue, namely the presence of events that fundamentally change the game's strategy (an opponent suddenly appears from an unexpected place, a Necropolis is built in a graveyard, etc.) and how the player reacts to these events. Mirror matches are less intriguing in this regard.
In general, my rating of map templates is as follows:
XL+U > Jeb > Diamond & MiniNosta > Mirrors.

3. I prefer high-quality gameplay where the player has time to think things through and calculate, rather than constantly making mistakes due to a lack of time. However, if they can play quickly and well, that's even better. Based on these considerations, I would adjust the timer value.
While the player is thinking, I personally try to imagine what I would do in the same situation, and then analyze my own and their decisions.

4. Yes, that would be nice, I agree.

5. That's also not bad. But I don't see anything wrong with thinking out loud (what you called "rambling"). It's possible to understand how the player came to a particular conclusion. I also haven't noticed any situations where phrases become repetitive.

6. Almost any time, you can find some interesting stream, and planning matches and creating schedules seems like an impossible task, at least because it depends not only on the streamer but also on their opponents.

7. Diablo streams from Amilu and Aive, and poker streams from Mizrael during their opponent's turn, were quite well-received. I don't like Hearthstone, but even that doesn't bother me.