Sending Yorktown east might have concentrated Japanese escorts

Would a radar-equipped USS Yorktown with the Eastern Fleet draw a Japanese carrier away from the Kido Butai?

Probably not, but it could make Japan concentrate escorts and treat the Philippine and Malayan operations more cautiously.

Japan would probably not divert a major carrier away from the Kido Butai simply to answer Yorktown's presence. The more plausible effect would be greater caution and tighter escort concentration around invasion forces. The Philippines would retain higher Japanese priority than Malaya because Britain was already heavily committed in Europe and North Africa. The counterfactual therefore changes risk management more readily than the basic Japanese operational plan.