Could an escort carrier have saved Force Z?

Would even an escort carrier have changed the loss of Force Z?

Probably; radar warning and a handful of fighters could disrupt the Japanese strikes long enough for ship defenses and land-based fighters to matter.

A fifteen-aircraft Avenger-like carrier with six to nine Hurricanes would not need to destroy every bomber. By disrupting coordinated attacks, warning the force, and calling Singapore-based fighters, it could make evasion and shipboard AA more effective; the assessment is that Prince of Wales would be damaged rather than sunk and Repulse would probably survive. The carrier's radar and communications would matter as much as fighter kills because they could start the response earlier. The counterfactual illustrates how a small aviation detachment could change the coherence of an incoming torpedo attack without defeating the whole strike.