that the simple solution for Pike now would be to still go through with warning everyone and preventing everyone from being involved in the accident, himself included, and simply retire or go into hiding on that day to set in motion the events that would lead to Kirk being in command of the Enterprise.
That's covered by Future Pike's explanation, I think--he might be able to get Balance of Terror to go properly, but Spock would still get killed some other way and without him a Federation-Romulan War always manages to happen.