Saber also won due to Gilgamesh not expecting her to have Avalon.The reason Saber beat him was because he was fucking around flirting instead of fighting seriously.
Changing my vote to avoid making problems for ourselves. EMIYA is not interested in winning the war, and Shirou is still the person he wants to kill.
You do realize that having Kiritsugu do an affinity based summon doesn't require it to be affinity with Kiritsugu himself, right? Just have someone else stand where you would normally place a catalyst to summon based on that person's affinity.