Tournament without a timer.

I would just play with a normal turn timer. One where top players can still make their moves in the late game.
For example, 8 minutes per turn on a strategic map in the late game is clearly not enough. Even top players don't have time to complete their turn if there's no buffer in the timer. And there are "thousands" of examples on streams.
If you set a normal turn timer, then an infinite timer isn't needed.
And I think that in such a tournament, you could add a rule - "once per game, you can revert a save due to a stupid mistake." This is about deleting an army on a fort. Or splitting up the main hero with a speed lower than that of ranged neutral creatures. That kind of thing. (if it's about having two morale levels in a dungeon on seven units - the difference is that we're talking about an action that couldn't possibly be beneficial depending on the random chance - a clear mistake that ruins the game)