I like the idea of units not being able to heal on or near certain terrain, because this forces players to be more aware of terrain.
1 - First to navigate the globe gets +1 Naval movement.
I was surprised that this wasn't at least a tech boost when I first tried this in Civ VI.
2 - Early boats were able to get to the open seas.
I agree with others that this would lead to save-spamming. Instead, what if the early ships crossing an ocean tile had a high movement point cost and a large damage cost? Large as in more than half of the ship's life. Of course there's still a chance that a barbarian ship/archer will sink your ship on the other side of the ocean
3 - Map trading -
4 - Tech trading -
Yes, I could see these as being a useful way to catch-up on a difficult game.
5 - Wonders that were grand -
I actually prefer a higher quantity of less-grand wonders because it makes me less frustrated when other Civs beat me to them
6 - Spies as units -
Yes! While we're at it, can we make missionaries and apostles non-units, since religious units mostly care about city-conversion anyway. I miss using spies to reveal all enemy troop positions.
7 - Unit gold from deleting -
Yes.
8 - CIVIL WAR! -
This might be fun as a SP scenario, but I'm not sure if I would want this in regular games. Especially MP games.
9 - The space race landing -
Yes! Then it would be a space race victory and not just the production victory that it currently feels like.
10 - The unit stats -
YES! In fact, didn't Civ IV also have an event log for the history of the game? Sometimes I would scroll through that and compare city settlement dates.
11: True huge maps.
I like the idea, but I suspect that anything larger than Huge leads to performance issues on most players' machines. Also, you would probably need to play at marathon speed just to explore/conquer the whole map.
12: The option of a map not only connecting East to West but also North to South.
Yes!
13: Transporter units (instead of embark).
Nah, that would bring us back to the stacks of doom from Civ IV.
14: Option to exclude city states from the game.
That's not in the advanced menu?
15. Option for vassal states.
I have no strong opinion on this.
I'd like to add a few of my own:
16. Barbarian cities - in Civ IV, barbarians founded cities which you could keep if you captured them.
17. The diplomatic relations graph from Civ IV - this graph showed contact, open borders, war, and defensive pacts as colored lines between civ leaders.
18. A "Generate Map" button in the World Builder - maybe I just didn't find this yet, but it sure would be nice for map script testing if I could re-run the map script with a single click and remain in the world builder.