So I just had a thought...
People scream in absolute terror
Anyway, Saber and Kiritsugu were completely unable to cooperate due to her Honour Before Reason
mentality versus his Combat Pragmatist
methods. The fact that Kiritsugu bent over backwards to not even speak to her probably didn't help. He was convinced they couldn't get along, so didn't even try to do so...
but what if something had changed... what if the two of them had been able to just sit down and talk for a second. Saber may not have liked his methods, but even she admitted he deserved the grail. As for Kiritsugu, if he got over his own disdain for Heroic Spirits, maybe he would have been able to find common ground with her.
I'm wondering if such a story would be possible. How much would Fate/Zero
and even Fate/stay night
change if these two were on the same page. They nearly won while barely communicating, so powerful a team would they had been with better communication without needing Irisviel to act as a mediator.