1. 6 minutes is definitely preferable. The reasons have already been stated, and I won't repeat myself. Sometimes I can't manage in 4 minutes because 1) I'm not very good; 2) I want to improve.
BUT: some people can manage in 6 minutes – why take that advantage away from them? Those who want 6 minutes can agree on it, and the rules can state 4 minutes.
I suggest a compromise between 4 and 6 minutes:
We play with 4 minutes, but each player has the option to load their autosave N times (for example, N=3, or N can be discussed before the game...) and finish the game.
2. Resetting to turn 116 during a match is nonsense.
I remember when a player with 40 upgraded bows and other things appeared on my opponent's starting town at turn 113. There were two options: either try to defeat him with a difficult combination of units or reset to turn 113. I chose to reset to 113, but what if that wasn't possible? My pride would have been hurt, and it's a ridiculous rule anyway.
3. Building 3 levels of magic in two castles when you don't have a 4th castle, but really need it, is nonsense. I will never do that; I'll just discard the scroll.
It's all just my opinion.