Its very similar to one response I saw when it was suggested that if a rotating CAP had been operating above force Z then the Japanese would simply have escorted the bombers with Zeros - again the problem with this answer is that OTL they did not although they must have appreciated that there was a possibility of the British commonwealth air forces doing just this - yet OTL they still sent their somewhat fragile Rikkos out in groups of 9 to 18 aircraft without escorts!
The RN had done studies in the early 30's that set AA policy and equipment for the next decade. Aircover was key in that it forced attacking aircraft into tight formations where AA fire may be more effective. If fighters had been present over Force Z then it may have ended up more like the Channel Dash where fighters decimated the torpedo bomber's attack.
Managing The Aerial Threat: Provisions for anti-aircraft warfare during the 1930s, Philip Pugh