Victorious was meant to teach the Implacable refits

Would an Implacable-class carrier have been better to retain than HMS Victorious?

Possibly, but Victorious was selected first so its modernization could teach the Royal Navy how to refit the Implacables; the unexpectedly long and expensive project consumed the opportunity to continue.

Victorious was chosen as the first step in a planned sequence of carrier modernizations. The Royal Navy intended to refit the best surviving Illustrious-class ship, learn from the work, and then apply the lessons to the Implacables. The Victorious project stretched to roughly eight years and cost far more than expected. That delay and expense removed the money for the follow-on ships.